Dan, I live in your neck of the woods (woking) and have a mate who used to come home from uni in the holidays and work for a company called 'Surrey Business Watch'. From what I gather its simple security work. It can be unsociable hours but he told me that all they did was sit in an office somewhere and watch tele, with occasional breaks in-between to do their "security" bit, which was just wondering around the building for a while! Sounds ideal to me
I don't know exactly how much he got paid but I do know that over a week during last xmas putting about 10 - 12 hrs in a day he pocketed about £1000. So I guess if you put the work in then the money is there to be had.
Good luck with it all.
Guy.