You can always take it to the local Council's mot place they will be very thorough as they do all of the registered taxis
The indis use a local MOT garage or two which they know.
I live in Guildford and over the years I have got to know a few garages who I don't mind letting them do a MOT on my 4200 but I always wait while they do it and tell them not to use the rollers to test the brakes to which they respond that they already know (when they enter the reg no they get a warning that the car is equipped with a LSD)
Also I make it very clear to them that they will not get any repair business from me beyond tyres and Hunter alignment... End of the day it's all about managing each other's expectations