TRD (Turner Race Developments) in Stroud.Very honest, enthusiastic and knowledgeable on all high end + VAG cars.They have been looking after my GTI for the last couple of years.
Have used Vee W services in Bedminster for the last couple of years with very good results on general servicing, mot's, dsg service etc. I think a good sign is that I've only ever seen VW and Audi cars being worked on there.