We use Wolf boxes at work in the back of most of the vehicles and to be honest mate you're probably better off with really useful boxes. Wolf boxes, sure they look the part and they may be slightly more robust but to be honest the average civvie user is not going to even approach the design envelope of these boxes so save the pennies and but really useful boxes instead.
I like the Peli cases. They are indestructible. My local army surplus place gets them in. The large ones are about £50. OK you have to pull the foam liner out as they have had nuclear warheads in them or something. But they are as good as new and a third of the retail price. Totally watertight and probably bullet proof too. I'd get another one or two if I had the cash lying around. Great on the roof rack.
Anchor Army Surplus. They have a place in Nottingham and Codnor, Ripley near Derby. Price and availability does vary as to what the Army are chucking out. But they have huge stocks of all sorts of stuff from Jerry cans to tracked vehicles. If you are coming to Lincomb you can have a look at mine.