From the RAC (https://www.rac.co.uk/drive/advice/legal/what-does-sorn-mean/ )
Can I drive my car with a SORN to a garage for an MOT?
Yes, you will be able to drive the car to a garage for an MOT appointment - even with a SORN in place.
However, it's important that the MOT has been booked because if are stopped en route by police and questioned, you can explain the situation and the garage can verify your appointment.
Be warned - you can only drive a vehicle with a SORN on a public road to attend a pre-booked MOT, or another testing appointment. In any other circumstances, driving a SORN vehicle on the road risks a maximum fine of £2,500.