That's a Phase II Vanguard. The Phase I had the round back up until 1953 and then the Phase II with the 3 box shape came in. It was replaced by the Phase III in about 1957. The RAF used all three versions including the estate version for QRA.
An airconditioner suggests an export model as they were quite popular in Australia. It could well have been brought back by a returning serviceman or just a traveller.
There may well be a couple deep down in the Indian Ocean when a number of cars travelling as indulgence freight had to go over the side when one of Her Majesty's carriers had to do a 180 for Brunei and cancel its voyage to Portsmouth.