ROB, I concede that the Plantagenets (Angevins, actually, at the time, I didn’t make the appropriate distinction) ruled in Anjou, somewhat to the west- southwest of Troyes.
I only mentioned that he lived in the Rhineland. I’ve read opinions that Rashi lived in Trier, not Troyes, and Trier had a significant Jewish population at the time. Either way, even if I am wrong, Champagne and the Palatinate are geographically very close. they are both North of the Latitude of Switzerland, which puts them in Northern Europe as I wrote. Rhineland traffic and Ardennes traffic flowed along the rivers, generally north to the North Sea. But as an exporter, (wine was one of the principle elements of trade at the time) Rashi would have encountered many people and words that were uncommon. Also, there is a mesorah in my family that Rashi’s 3rd daughter married someone from Iberia (Spain), so he would have had at least some give and take with the area.