First off, the whole idea of "languages" as a consolidated concept was still a little vague in 1200. Every valley, every backwater, pretty much every county had it's own distinct accent, and some their own dialect.
There's a story (written about this time, in Olde-Middle English) about a man who was caught in a storm in the English channel. He started in Dover, and was washed ashore south of Newcastle. When asked (in the Northern English Dialect) if he was all right, he replied "I'm sorry - I don't speak French". {insert medieval equivalent of a rimshot here}
For example, France at this time was only just unified, and other countries had a long, long way to go before anything like a sense of national unity - and thus a single national language - were starting to form. Normandy, Aquitaine, Parisian, LangDoc - almost every County had it's own "language". Add to this the complete lack of telecommunications and you get zero "normalizing" effect - every dialect was proud and distinct, and rarely heard each other except when some "tourist" wandered in to town. And, to a large extent, mostly unintelligible to others, so less of an "accent" than a different language completely.
Here's a graphic of the 6 basic language groups of the Iberian peninsula (Spain) - yes, 6...
erzo.org/shannon/ars-magica/ ... guages.gif
With local dialects and such, it could only get worse. Anywhere, each separate political entity tended to spring from a separate language or distinct (and proudly, fiercely independent) dialect.
Now, this creates a REAL headache for RP - especially with your average, typical Player Character who wants to speak directly, never thru an interpreter - but that's how it was. Unless you found someone "educated" (which meant they spoke Latin) or you had a guide i[/i], you were just SOL in the communication department (or had a spell - yeah, well). Personally, I find the concept appropriately challenging - but not everyone wants to deal with all them darn furriners.
Here's a period political map of Europe. With some creative interpretation (esp in the Holy Roman Empire), each political division can be seen as a language division:
euratlas.com/history_europe/ ... _1200.html
While that's a coarse approximation, it can work - or you can ignore history and just call all of what is now France "French Speaking", instead of the half-score or more of unintelligible dialects that, over the centuries, became what we now know as the modern language "French".
Your call, have fun.