As Loosehead states, you can drive to and from a
pre-arranged MoT test:
http://www.direct.gov.uk/en/Motoring/OwningAVe hicle/UntaxedVehicle/DG_069727
Some MoT test centres simply book vehicles into their diary with an entry like "0900 Smith MoT". If you're going to be driving an untaxed vehicle to the test, you'd be well advised to ensure that the garage records the
registration number of the vehicle in their diary, so that they can verify your appointment if asked to do so by the police or DVLA.
Chris