Garage needed in South London / Croydon area

Hi all,

Iv'e got a Mk1 Golf cabriolet in need of repair.  I've got a real problem with performance (slow to accelerate) and the exhaust is phut-phutting when I ease off the accelerator.  Possible misfire?

I was wondering if anyone knew of a decent garage to get this kind of problem fixed in the London area, ideally around Crystal Palace or Croydon area

thanks,
Mike G