I am not sure that part of England/Scotland has mineral wealth or caves. I could only find a lime deposit quarry. In a fantasy setting we could have a mine there, but that would probably mean it would be the only mine there...and everyone else would want it (including local lords, rival covenants, and both kings). It would be quite a militant campaign.
How about this? Make it a new mine of iron, that the covenant would need to exploit and defend against all comers? Ultimately this would make it impossible to sustain and we would have to chose sides or some such.
After you said that I took a look, looks like it's totally devoid of anything valuable to mundanes that was available at the time.
But... has a LOT of cool looking crystals... blue fluorite and dolimite... could have magical mineral deposits is my idea. Not rich in money, but maybe rich in components Shape and Materials and Vis. It would be a motivating factor as to why we would suffer lack of amenities.
Looking around the area, most of the quarries seem to be for stone for construction or slate, with a little coal and iron in 18th/19th centuries - so if you want mines, we could have the modest anachronism of finding workable coal/iron with medieval technology, or we could use the "fake mine" option - have a lab text for creating stones or metals, a source of Terram vis and we quietly magic our resources up saying "who knew this remote valley had such good resources?" It's an obvious trick for magi, and only requires that one of us be a Terram specialist.
Of course, we could then apply this to magic weaving (turning wool into cloth is a high-value part of the economy), tanning (leather and sheepskin), glassmaking (sand into a high value substance magi use a lot of).
Trusting wikipedia, the Romans mined lead at Alston Moor, which seems to be within Cumbria borders.
en.wikipedia.org/wiki/Mining_in ... Mining.jpg
Furthermore, there is an iron mine, closed in the 1960s, in Hodbarrow RSPB reserve on the border of lake district, also in Cumbria.
en.wikipedia.org/wiki/Hodbarrow_RSPB_reserve
Gold, I think, would be an anachronism anywhere in England. Silver might only be in the South, but I don't think iron would be a stretch anywhere in the North. A bit of magic might allow us to mine deeper and better than the mundane miners, giving access to minerals which have been neglected in historic records.
True, a mine may be valuable and attract attention from the nobles, but if it has a reputation for being haunted, it may not be so attractive.
I am not sure if the area is sufficiently mountaneous to allow sizeable caves. My experience from Cumbria is limited to the M6 
The Alston moor is an interesting choice, but the kings did charge rent because of silver found inside the lead/zinc deposits...which suggests probably its owned by a lord or the crown directly. The Hadbarrow one is way later around 1850s, made with 'modern' excavation technology. Lets keep both in mind as options.
I have been assuming that there must have been lots of small mines around the country, not necessarily operating for a sufficient duration to be noted in history. The ones we know about are the prosperous ones, lasting for a long time. But this is of course conjecture, I don't really know anything about medieval mining.
The two mines I pointed to are mainly evidence that the resources exist in the general area. A mine which was promising, but quickly abandoned because it was haunted, is plausible in Mythic Europe. The magi may well handle the haunting better than mundane miners.
A prosperous mine is difficult, pretty much of the same reason why a castle is, it attracts attention and is worth fighting over. A small and insignificant mine goes under the radar, both to contemporary lords and historians. Making a claim to Alston Moor does not seem realistic for a Spring covenant.
I have been drafting a bootstrap adventure based on this idea, with a Winter Covenant which is ripe for resettling with young blood for a new Spring. I shall be happy to run it if you want it, but don't want to bash in or overrule the original volunteering SG, and I certainly do not want a long-term responsibility as alpha SG; it is just an offer for the startup. The starting point is a group of young magi adventuring towards the wild and mystic North in the hope to find unclaimed resources (vis, etc.), possibly with a Redcap making introductions to bring the group together for the purpose.
Clearly, such an approach would introduce and fix a number of locations and people, but the idea is to minimise such decisions, leaving details to be agreed later.
I was distracted by the crystals lol.
I was floating an elementalist Idea. Posted the core concept on the Character Designs thread of the main forum. Aurum and Muto specialisation With Elemental Magic. I could go that route. But that particular build really needs a look at and approval imo. I don't think it's broken, but it is highly 'customised'.
It wouldn't take long to breed some precious metals... aka take a useful Terrem ritual. Though breeding elementals would be fun. Lol.
Btw if my ideas seem outlandish, I've a lot more free time than I'm normally used to so I've been making characters for a possible RL game. A lot of characters...
My magi concept is an ex-misc native Cumbria tradition with very few remaining members. He is a kind of "wildman" with "way of the Fells" and wilderness lore. He was trained in a covenant with only his Pater as a resident magus. That pater dies just before gauntleting my magus and he is looking for other magi to help him get through his gauntlet and too live with. This covenant could be the Winter back to Spring setting and would most likely be in a rural setting given my magi' skill set. My magi would have no real idea of what is available as he was not taught the command word etc as he was still an apprentice. That would give a reason for the place and an existing mundane relationship allowing occupation of the land, along with minimum numbers of highly warped covenfolk.
Any use a concept?
I think it is a splendid idea, and it can be combined with many of the other ideas mentioned. Expanding from one magus to six, however, is major task. Equipping laboratories for all the magi will take a lot of time. I am not really up for a no-lab, no-book kind of saga. We have heard very little from the SG; does he have a story to start with your concept, and take us to a decent Spring covenant?
BTW. What is the Hermetic inheritance legislation like? Who inherits a dead magus/covenant? Or maybe this pater had a will!?
My magus is effectively unable to write in Latin (Latin score 2) as his Pater was also very poor in his understanding of Latin so any will would be in English and therefore unreadable by most and possibly inadmissible as valid. As such both truly qualify as "Hedge Wizards". I was thinking of taking Dark Secret (Not gauntleted, therefore not a full member of the order) so his stance will be he is the last magi of the covenant so it is his. This may (probably will) come back to haunt him in the future so good stories all round.
If we go with this concept, the covenant also has a stake in the dark secret, effectively a hook, or more. I am happy with that, but we need to be clear about it.
On another thought, I wonder how much of a secret this is. I am sure the quaesitores and redcaps have accurate records of gauntleted magi, and you don't have a sigil. I cannot really see you passing as a magus where it matters, i.e. where quaesitores are involved. In fact, it sounds more like a major flaw, than a dark secret. It is a plausible background and interesting.
Whistler has to be his buddy. The two of of them know everything happing in the wilds and unable to tell anyone. Animal Ken and Mute, raised by wolves. Just a boy and his dog.
Note: I fully don't expect to play anything until we are doing more formal character approvals.
It could be... some one someone finds a cave with neat rocks and says "wow I gotta tell my Verditius Friend about this..." then the two stay a bit, and now have say a little hut and are like. "We'd rich, swimming in Vis and making super talismans... if only we could."
"We need an elementalist or a terrem..."
"Hey, I know someone, but she's a little weird. Blind..."
"Blind and mining with all that precious... we don't know how deep that goes!"
"She's all we got."
So now it's 3 of them, blind leading the blind. So rich if... if only...
So after a month or two... digging big holes with terrem for living quarters, but it's slow in this environment. (I'm assuming bogs and peat or is it hilly)
Anyway so the wild man is like wut, smoke? A hut? Wait that was Latin! He and Whister are watching them for a week... they are hopeless. "Maybe I could help and they could me with finishing apprenticeship." He can't believe his luck.
Maybe a season passes, but this really is an adventure trying to dig and mine. Wildman befriends us, we befriend him, after a bit the blind elementalist asks probing questions, her Intellego magics picked something up. We talk...
We decide to form a covenant, you to get apprenticeship, other guys to get rich, Aella just wants friends, Whistler a sandwich. But how can we make this legitimate and legal...
Ugh we need someone with ties to the Tribunal, enter all other Magi because it's really hard to keep a hush on things.
We promise said person(s) helping us with legality the world. He comes out thinking there is an existing covenant. He packs everything. Personal library, lab, some servants, and a sofa. Ok not a sofa, a Persian rug. Authentic, it took two old women their entire lives back to back to make this.
He gets out in the middle of this bog or hills, sees the 4-5 of us, a hut, a dog and a whole lot of holes in the ground.
He's mad. He rants, raves, talks about his sofa... I mean Persian rug. Then we show him the goodies in the cave. He says "Where do I sign?", "I'll need a more comfortable arangment, my sofa. I mean Persian rug could get dirty, it's authentic..."
(In case someone played an older established Magus and so would get better things)
It really writes itself.
A couple of alternatives,
- We assume that the old ex misc swore (some of) us into the covenant prior to dying/disappearing. This may or may not be true, but it is unlikely to be investigated. The nature of the old magus indicates that the covenant was not made in writing anyway. (This works with any Winter covenant rejuvenation.)
- We go by the Tribunal Border major hook, and take the challenge of sorting it out with both tribunals over time.
- We just assume that it has been sorted, and start playing with a covenant designed by the rules.
There are a couple of hooks which play on multi-site covenants, ruins of dead covenants, chapter houses, etc. Would such hooks suit us?
Question. Are we going to roleplay the founding? Or should we make the covenant by the rules and start from there? I think this is an important question.
Summary.
As far as Ii can see, three players have posted concrete character concepts:
Reynard le Blanc ex Tytalus (T Riffic Rex)
Magnus of Verditius (loke)
an apprentice ex Misc (John Graham 52)
What is the time frame for or approach to deciding? What pace do we expect onwards?
Sorry for being so talkative. I have ruptured the Achilles tendon the other day, so I don't have too much else to do 
He's not an apprentice, he's a magus with almost 15 years apprenticeship behind him and no parma magic. he does have a sigil (he shows off his big warhammer). "Who say no good? me show now, RiGHT NOW!, miguss not push Cearnos around. He show who migus, he has spills and every something" - Latin 2 here we come.
I will be off line for the next three days as I am away cooking for a Live Roleplaying event near Carlisle and I don't think I'll get a wi-fi signal. keep posting 
Same, with the second one. Lots of time.
I'd actually rather Aella, but she would need ironing out the feasibility of blind or really the rest of her. I can easy swap out blind for something else, actually think I should and disfigured actually has a kinda sad description. Swap Fury for Wrathful, Blind for a Story Flaw, and Disfigured for Judged Unfairly. https://forum.atlas-games.com/t/familiars-from-the-start/246/1
A character like Reynard may get bored, he wants to hoodwink and steal for the fun of it. A character like Aela would be happy because though it may be a dank cellar, it's her dank cellar. Or hill top or what not. With Age Quickly and needing to find other Magi to do her longevity ritual, she's instantly loyal.
If she isn't feasible for this saga, I can put her on the back burner, lol. I think I'm just stuck on trying to figure out what a blind hermetic Magus do. Either way, I would be fine with playing only a few years out of gauntlet, if we wanted some older Magi and stagger power level.
I'm pretty sure I'll be the most available to post, but I'll settle down to whatever pace we set once we get started. We'll have to see what the rest of people and head ST wants to do. Roleplaying the covenant start is fun, but personally I've done it a bunch. Also if there is any character conflict it makes sense for the character to walk away and can hiccup the start.
I vote for starting after the covenant is formed. Though it doesn't have to be fully built with amenities in my mind, I'll take the "less experienced Magi gets the dank cellar and likes it". Depending on the stories to be told it may make sense to do one or few years of our character's "settling in", starting half built, iron out the logistics and social pecking order, then progress a year or two to finish spending build points.
I'm actually not well versed with doing covenant building via build points, so I'd be learning. I just recently got Covenants and haven't looked through it. Most my experience is 4th ed. The 5th ed I have played has had a lot of house rules, so if I'm dead wrong about how something works, bonk me on the head.