it is so slow its out of this world 2 days ago t would not go past 50mph , but prior to that it was still slow struggled to get to 70mph, a week ago l thought it had cleared it self because it went fine drove like it should do but this only lasted a few days now back to being very slow again ,its got nothing to do with surrendering to crap bmw is as ive got a bmw 323i on my drive that wont even start yet again
any help would be welcome

Have you tried changing gear?

Could be related to the lazy attitude of the French, however, you may want to check for a restricted exhaust. Sounds like your cat has dropped it is innards into the muffler and choked it.