It's very different with buses/coaches. DVSA inspectors test the vehicles at an Authorised Testing Facility (ATF), which could be an operator premises that has been authorised or it could be at an external maintenance provider such as a Volvo or Scania dealership. It's not like a car garage where they employ an MOT tester directly and do the tests. Certain facilities have to be made available to the independent DVSA inspector, and an ATF's own staff cannot interfere with the test. Generally an ATF has to book tester slots with DVSA and then they sell slot spaces to operators, so an operator ends up paying the DVSA test fee plus a "lane fee" to the ATF.