Thanks everyone, some interesting thoughts here. Definitley not a Shorts 330, that’s a type I could ID. I feel I ought to add that the a/c was quite close to my position, almost over head and fortunately made a turn, banking towards me which is what confirmed it as a biplane. Unfortunately its height was such that I couldn’t determine the number of engines, except to say that the nose appeared smoothly rounded and unlikely to be carrying the large radial engine of the AN-2, although the colour silver/alumimium matches the AN-2 described earlier. The sound was, in my opinion, a deep “old sounding” rumble. I was so enthralled at the sighting that I completely overlooked the configuration of the tail assembly.
Once again thanks to all for reading and taking the trouble to reply.
Robin.