I think the SARAPETA You are looking for is the one that served in a variety of roles I believe she was a German coaster given the the RN after WW2 I heard somewhere that she had been fitted with 2 torpedo tubes and U boat Periscope to train U Boat Captains she served with the RMAS as TRV on the Loch Long & Arrochar Torpedo firing ranges i think she went for scrap in the early 70s.
Dave