I am sure most people are aware of this but here is a PSA if not.
Your local council almost always has its own MOT test station. You will usually be charged the full VOSA MOT rate however you can guarantee that you will get an unbiased test.
Unless I know and trust the garage I often wonder if some use MOTs as a way to drum up a bit of business.
Link to find your local one -
http://www.ukmot.com/Council-MOT-Test-Centers/UK