Thanks Tiggy's Mum that would be great.
I've added him to the animal search and will look at the national pet register.
I talked to the rescue I used to volunteer at and they said they were really busy over the summer and couldn't do anything to help him. They also said they could only trap him check him for a chip etc then release him back to the site but not till later in the year. As my work is probably going to be moving premises after Christmas I won't be around to feed him. Do you think it's worth asking other rescues or will they just want to do the same?
Part of the problem with him is that I hardly see him, last week when my colleague saw him he hadn't been seen for a month. I think he stays hidden in the day which is pretty sensible but all the food I put down is being eaten.