Like I say, I'd list him as found, he could well belong to someone may have been missing for a while. Doglost is the place to start by listing him as found, I'd be really surprised that he didn't belong to someone.

It would be a shame just to hand him in to battersea or handing him over to the dog warden, without trying first to find out if he does indeed have an owner - Scenario, what would you do if you happened to have lost your dog (could have escaped, been let out by accident, stolen & dumped etc...) wouldn't you be slightly angry if you later found on he'd been handed in to the local pound or handed over to the dog warden....

Just a thought....