What "languages," in the modern sense, were spoken in Medieval Europe?

I'm writing some fiction set in Iberia circa 1100 AD. I need to know about which languages were spoken in Europe at that time.

The contiguous area where indo-european languages were spoken naturally forms a linguistic continuum; thus if you wanted you could divide languages very finely or more coarsely. What I would be interested in would be a list of languages, not mutually intelligible with each other, such that everyone in the area of Europe reasonably close to Spain could be said to speak some dialect of at least one of them. In order to be useful I'd prefer if this was a fairly coarse characterization.

Some questions that are involved in deciding what such a list would contain are:

\-To what extent were closely related circles of languages, like Castilian, Aragonese and Mozarabic, or Old Dutch and Middle High German, mutually intelligible?

\-Did North Africans and other Muslims generally speak Arabic or their own ethnic languages?

\-How long of a list would be necessary to cover most of Europe at the time?

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I would also appreciate any good references on these topics.