Hughes, the yellow Exploder may well have been G-LNAA, the ex-Lincs and Notts Air Ambo, which PAS use as the backup for the Trinity House contract. I have to agree that they are much more pleasant neighbours than the Exeter 117C2, though.
btw - you must've been out on Dartmoor at a different time from when I was walking the dogs. Couldn't see hand in front of face for all the horizontally-arriving wet stuff; wouldn't have wanted to be VFR around Cox Tor/ Princetown in that.