I always have mine done back in Bournemouth since my family have always used them. Lovely little garage.
My advice would be to avoid anywhere that offers these silly cheap MOTs (30quid sort of thing). I understand that it costs the garage more than that to issue an MOT certificate and therefore, in order to make profit, they will fail it on things it didn't need to fail on - safe in the knowledge that you will almost certainly use them to carry out the work.
family. Or just get a bent one like me*
*I've made this up of course.
They tend to value their MOT testing authorisation and really don't want trouble with the Feds.
A little common sense also goes a long way. If they fail it for worn brake pads, for example, you can go and ask to look at the pads before authorising them to fit new ones. It's trickier if it fails on an emissions issue, because the lambda sensor isn't necessarily going to look obviously broken.
In short, you'll probably be alright because generally they're not out to rip you off. If they decide they want to, however, you're buggered.
or take it to a independent place that only do MOTs (and not remedial work).