I know they can be a bit expensive and all - but the one I have local to me really do know what they are doing. And are really quite good to me - I think?
I had a sebring exhaust fitted to my golf with Halfords (cos they were cheaper by about ?20/?30). They fitted it on and within a couple of weeks it was beginning to rattle at certain times. It also didnt look very straight. They took it back had a look at it and put it down to the design of the car. Took it back once again and they told me that there was not much they could do since the Golf Mk3 does 'flex' quite a bit and that their was not much esle to do but for me to put up with the occassional rattle.
Took my car for a service with the local VW dealer yesterday (doing a ?99 deal at the moment) and I asked whether they could have a look at the exhaust for me since it was rattling. Got the car back from its service and they had also fixed the exhaust up for me too. Not only does it not now make any rattling sound but it also looks a lot straighter than before too. Now I have no rattling noice at all.

There was no charge only for the service.
Not much of a story - but until I can find someone else who can just be honset with me - then I dont mind paying that bit extra. As for Halfords - well they may have saved themselves the short term cost of having to bother to get my car back up the ramp again and attempt to fix the problem - but in the long term they have now lost a customer!
When will they ever learn?