UPDATE
SULLY'S HOME!!!!!! (well he was last night at 8pm)
Heard a constant miaow on my walk from behind a garage door and I knew it was him! Went to the person's front door, they had actually called us to tell us that they'd looked, went in and he appeared from under a boat. Poor chap was so scared it took a while for him to recognise me (before I then burst into tears). Held so tightly onto him whilst walking him home. He's now tucking into food, cooked fish especially - the other 3 were glad of that too!