To be honest I cant get any good deals on locks, so was only buying from B&Q and selling on. Your best getting a lock yourself, then you can pick one that suits your price rang. A simple 50mm padlock to one of thoses circular locks will fit. The holes size is 9.5mm. so somehting about 8mm will be fine. I'll look out for your order.
This is the lock I use. Cost about £15 from tesco. Seems like it's very good quality. I'd imagine the weakest link in the whole lock would be the steel supplied by uber (not a criticism at all, very happy with it), so anything more would be overkill in my opinion. As we always say, if they want it enough they'll have it.