I'll mark their location on a map with notes on aura rating. Did I find any high level ones? Either way, I'll share my observations with my sodales.
As stated, Benedict scouts each morning in Eagle form, scanning the roads and countryside through which the day's travel will be. He has no particular urge to visit London now, though he will return later on his own, once they are settled in.
Obstetrix wouldn't mind going to the Fair. Or at least, letting the grogs and companions go and enjoy it.
Ruedi would rather stay at Betula's side. Unless she assures him she'll be fine with the other Magae.
The eagle sees essentially what the vulture sees, except that it cannot detect auras. There is a lot of wilderness which could hold sources of magic, or fay, but it would take months on foot to find the right one.
EDIT. Cath'rinne finds auras up to about level five, but nothing spectacular.
The group make a leisurely pace into the town. Other travellers seem to have enough with themselves. The grogs pull the wagons up in front of a wheelwright. They need new spares after weeks on rough roads, and make a bargain with the wright. When he sets to work, they ask to be excused to have some free time at the fair.
In the meantime, the magi and companions have a chance to orientate themselves. The market is dominated by craftsmen, most of them selling wares from stock. A potterer and a wood carver stand out with excellent and beautiful products. Then there are studs for rent. It is just the season. And in between, the odd wise one selling folk charms and potions, and the peddlar with goods from afar.
While you stand there, wondering what to do, you hear a commotion on the other side of the ground. Two armed riders can be seen above the stalls. A small crowd is pulling away from the scene, and filling up the square where you are. They are not running in panic. It is more like a prudent withdrawal.
Obstetrix will be watching from the shadows of some stall, her eyes looking at the peddlar there, to make sure to give him a smile.
Ruedi will take a step in front of Betula, and rest his hand close to his club, clutching his bow. He disliked having to use his club, so he preferred to be able to at least take one good shot if there's trouble, at least.
Gerhardt (the shield grog) stands behind Obstetrix to make sure no-one gives her any trouble, but he turns around slowly to take in the scene. Trouble already?
The peddlar returns the smile and looks the potential customer over. «What can I do for you?» he asks. «I have some beautiful linen, soap from Iberia, or maybe a comb. Look at the craftsmanship.» He smiles again, but then, all of a sudden, a grim furrow forms on his forehead, and he shuts up. His attention is still with Obstetrix though, waiting hopefully for a possible trade. You can still hear some commotion in the background, but the peddlar does not seem to care, nor does he mind the grog who seems more interested in everything other than his stall.
"Actually, yes, I would like some soap and some linen." She sees his grim expression, and asks in a low voice "What is wrong?"
Cath'rinne will encourage the companions to investigate the fair to see if there's anything out of the ordinary being sold, and to gather news from the land with travelers and merchants. She'll explain that she's especially looking for clues about the ongoing war against the Diedne, past battlefields, stories that point to strange phenomenons that may be worth looking into, or other traces of the supernatural. But even mundane news may be useful along the way.
A magical aura of 5 or higher is something that Cath'rinne is likely to want to investigate before they continue north, unless something else attracts her attention. She wants to have notes on several locations that could be considered for a covenant site when the day comes for the group to settle down, and she's also looking for possible vis sources along the way, or just places to return to for adventure with more preparation later on.
He turns to find the wares, watching Obstetrix out of the corner of his eye. «Oh. Nothing wrong,» he says. He shows you a couple of different qualities of linen, bleached and unbleached, cautiously but discretely holding his hand on the most expensive one. He quotes a price, for the linen and for soap.¹ He looks suspiciously at you, like so many parmaless people do.
¹ Roll a Bargain+Per to gauge the fairness of that price and Bargain+Com if you want to narrate the haggling.
The most promising one that she sees is about a day's march off to the West, without any carriage way. Departing from the road here, in the town, or ten miles further North seem to be as good as anything, if you want to go together. If she decides to go on her own, we make another chapter thread.
Benedict will wander the fair at Cath'rinne's suggestion, looking for anything being sold that appears out of the ordinary for a mundane market.
Finn will also wander the market and if a pitch is available he will try to draw a crowd to his storytelling to earn a few coin and maybe pick up a contact or two to talk local gossip with over a mug of ale.
There's no need to split the party at this point in time. 
The market appears to be above board, though Benedict does notice one or two stalls selling potions and folk charms. There is no reason to think that this is anything more than simple herbal remedies and the like, but then again. If there is a hedge wizard doing business here, it has to be them. A man in his thirties is bargaining over some wares at the stall.
While Benedict considers if he should investigate or not, he is almost run over by a crowd coming down the street. Looking up, he sees two mounted knights heading for the stall.
Only on a Per+Awareness 9+ will he notice everything that is going on. The customer looks up, terrified. He quickly bends down to talk to a little boy at his side, maybe ten years boy, and sends him away between the stalls before the knights arrive.
If he is less perceptive, he will only notice when the knights arrive, that the customer backs into the street, looking for somewhere to run. Alas, men at arms enter from several directions. One of the knights speak to him, with a loud and confident voice. «Stop there. You are arrested under the laws of Eadric.»
Finn finds a brewer who has set up a table and benches in the field. There is plenty of space around, and a juggler is entertaining when he arrives. Ale can easily be obtained, and if he waits his turn, Finn could quite possibly earn a coin too.
Cath'rinne may watch the arrest from above, if she is curious.
[Not sure where Betula is in the picture, @dc444 . Ruedi follows her, I think. I'll include you in the next scene regardless ...]
Cath'rinne is probably trying to remain inconspicuous in the cart.
Oh. I thought she was vulturising. She would need to step out of the cart when the wheelwright tinkers with the wheels.
Benedict is careful to keep a distance so as not to get involved, but watches carefully, wanting to see this dangerous law in practice.
Cath'rinne makes herself socially discreet, then.
Obstetrix will buy the soap and cloth from the merchant, and keep her eyes out on what is happening outside, but will keep silent, for now.