Are you serious? Ever been to France? It's teeming with Brits owning properties, especially in the western part..
Can't say I have had much experience with France, I have lived in Andalucia in Spain though, and the place was overrun with British, and in Britain nobody I knew would want to live in France and hated the place. There was never a need amongst the Brits there to speak Spanish, and many who had lived there many years barely speak a word. The ones that owned businesses though, did speak Spanish, as they had to (and were more successful there because of it)
I'm learning Polish because it's something I actually use (family, etc..), I doubt however it would ever improve my career prospects, unless I had a some sort of low-paying government job dealing with Polish who don't want to learn English.