I get the Martin Lewis Moneysavings expert weekly email. This weeks includes advice about saving money on our mot's. He recommends taking your car to a local council test centre where they don't do repair work, only test so have no vested interest in failing your car!
Hope this copied short cut works
http://www.moneysavingexpert.com/travel/cheap-mot?utm_source=MSE_Newsletter&utm_medium=Email&utm_term=19-Mar-13&utm_campaign=travel&utm_content=192#mapfinder