Have a look at
Tax officials deny claims that UK-French double tax treaty is to be scrapped from FrenchEntrée.com
NDS - News Distribution Service
UK/France Tax Treaty signed
http://www.hmrc.gov.uk/international/france.pdf
There are infestations of a v large British airline's pilots clustered around Nice (many), Toulouse, Bordeaux, some Paris, Barcelona/Alicante/Malaga. They do not seem to be unduly alarmed having seen more than one onslaught come to naught.
It should not put you off your idea, but it may be an idea not to let taxation rule your life and where to live. We will inevitably one day end up in a unified and taxed Euro-conglomeration. By all means make hay while the sun shines, but do not expect it to last forever. Foreign residency is a big step, and they make sure you DO cut your links if you are going to throw off the tax yoke, and they WILL examine you with a microscope. It is a major negative in life.
Me- I'd go to the Nice area. This could seriously be the most beautiful place on Earth! Every time I fly in or out, I can't help thinking it's wasted on the French! They've got too much like that- we should invade!