So got it tonight and was playing around with it to make sure it was OK. But noticed it kept restarting/rebooting by itself, so I started taking notes of all the times it did it. After 1hr17min it had restarted 15 times, yes fifteen in just over an hour!
So I had resigned myself that I'd have to be visiting the store tomorrow night, but decided I should attempt the inbuilt "Factory data reset" option (Settings > Backup & reset).
So I ran it, then used the phone for just over 2 hours with no restarts at all thankfully. I'll tell him to keep an eye on it for the next week or so but I think the handset is OK now. Although I am tempted to return it just in case.
Bit strange though obviously, anyone ever had similar issues with their San Diego? As I said before, I've been using mine for over a month now and not had any issues at all.
Edited by DaveSimonH, 13 February 2013 - 01:22 AM.