Thanks everyone for all the info. I have emailed John Haywood. Latest info from window cleaner suggests that it has been there since at least January. So I think its a good bet that it has a good source of food, loads of berries on the trees and has found somewhere warm to perch - possible the church spire or around the graveyard somewhere. I went out today and I couldn't see it but could hear it doing whistles and noises that were definitely not native in nature! I whistled back and got a reply in imitation. Seems a content bird, but of course has no partner, so must be a bit lonely. Can I sex it by just looking at it?