T Morris, in a comment to this post, asks why there are no English ‘translations’ of French place names, such as there are in other languages (Parigi in Italian) or as there are for English names in other languages (Rome rather than Roma).
In fact, there are English spellings of French place names that differ from the French originals, but they seem to be reducing in number over the years. We used always to write Lyons and Marseilles for Lyon and Marseille, and going further back in history, Calais used to be written as Calice. ‘The Jackdaw of Rheims‘ (one of the best-known Ingoldsby Legends) provides another example. As a (very) small child, I imagined that Dunkirk must be in Scotland, and Ushant never seemed to me to refer to a place in France (I think it is now usually seen in its French spelling – Ouessant).
The same thing is happening with other foreign place names – Saragossa is now usually Zaragoza, and Corunna has become La Coruña. As we travel more, we become aware that our spelling and pronunciation of foreign place names has got out of step with the native, and we adjust our version to make it more similar to the original. With spelling that is easy, but the pronunciation will still be an approximation, better or worse according to our individual ability to imitate, or willingness to do so. The changes take place particularly for those place names that have dropped out of our consciousness, and then come back to us – Flushing became Vlissingen when car ferries started to use the port more regularly, and Leghorn became Livorno when it became an easily accessible tourist resort.
The regions of France still retain their English names – Brittany, Normandy, Burgundy, Gascony show no signs of becoming Bretagne, Normandie, Bourgogne or Gascogne.
If we turn the question around, it seems odd that the French have so few spellings of their own for place names in the British Isles – after all, (Norman) French was the language of government in England for about three hundred years. I can find a handful – Londres, Douvres, Cantorbéry, Edimbourg, Cornouailles, Tamise (the Thames), and the names of the constituent parts of the islands – Angleterre, Ecosse, Pays de Galles, and Irlande, plus Grande Bretagne itself. The French pronunciation of English place names without different spellings is, however, just as gallicized as our pronunciation of French names is anglicized – as is to be expected.