I once got Chesney Hawkes's autograph in Sainsbury's. I didn't even want it, but it beat trouncing around the cat food aisle. Anyway... He was really nice and also a bit simple, I think: he spent about 10 seconds trying to yank what he thought was a lid off of the pen until I highlighted the fact it was a twisty.
I also got a Hollyoaks actor's autograph in Superdrug. I can't remember his name, but he played an incestual rapist father. He was nice, too.