I would personally suggest taking it to Munich motors out in Berkshire
They really know their stuff!
http://munichmotors.co.uk/index2.html
Coopers Cobham are the best by far in terms of stealers though, if you wanted to go the main dealer route.
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Previously: 2003 Peugeot 206 1.6 8v | 2006 E90 320d M-Sport, 19" BBS CH, Full Ice-cold JL audio install, August 2010 Total BMW 6 page feature car. | 2003 Nissan 350Z GT Coupe 286BHP
Now:2010 E92 LCI 335d M-Sport