Have a look at my similar post "WW2 RAF Ambulance Markings" there are some useful replies.
You may possibly find something in the Wellington Museum in Moreton In Marsh because Enstone was a satellite of the Moreton in Marsh airfield. The curator has also co-written a book about Moreton, of which I have copy somewhere about although I don't recall any useful vehicle pictures,neither for that matter do I remember seeing any in the book "Oxfordshire Airfields in the Second World War 2."
Another thing you could do,if you are local to Enstone ( I can virtually see it) is to go along to the local MVT meeting 4/5 miles away held at the Hook Norton Brewery on the last Thursday of the month. As well as the excellent beer .there are members knowledgeable about local matters and at least one with a WW2 RAF marked vehicle. Someone may be able to help.