Thanks so much for the suggestions- I will start with the olive oil today. Pickles has a good appetite (perhaps too good as he has to be fed seperately from the rest of the cats or he steals their dinners too!) so I think that will work well.
I never thought of the fact that he was injured being a reason for the dry skin- but that makes so much sense! The dry skin is mostly by his tail and with his broken jaw, which has healed but not perfectly, this may be the cause of his problems. He is such a clean cat, always licking his paws and whiskers, but he doesn't seem to do his back as much. He's also forever licking the other cats, but they don't reciprocate, which is too bad, they could help him out!
I'll let everyone know how he does, he is such a special little chap, and I am SO proud of how far he has come in the year we have had him. It always amazes me when a cat learns to trust again.
Louise