Wasn't the Army School of Transport there around that time?
According to 'British Army Units from 1945' Royal Corps of Transport, Longmoor was the home of the School of Transport from 1965. 12 Trg Regt was located in Buller Barracks, Aldershot.It was. I think in the guise of 12 DVR TRG Regt RCT..
You are much more likely to be right there Dan than I am. So cheers.