My brothers mate used to work at Racetech, who do all the Breyton BMWs and TTs. They had a few demo cars and this was one of them. It was sat in the warehouse gathering dust and we went to have a look at it, have to say the kit looks wank up close, its just bonded on, and it looks far from proffesional. This may have just been this particular one, but it certainly put my impressions of them down.
From reading things like Evo, there isnt enough perfromance wise to seperate it from the cup, although im sure with a rear engined RWD V6, the drive would be much more fun. Bear in mind that for what they cost you could have yourself something pretty monsterous.