Hi Patrick
We hired a tourer about 4 years ago when our van was in the repair shop for an extended period. We got it from a firm in Oxfordshire - sorry, done a Google search but can't find the details.
But be warned.......make sure you have a good look around the van first - the one we hired had loads of things wrong with it which we didn't find out until we got to our camp site! Most of the blinds were broken and some of the curtains wouldn't pull across either, one of the seat cushions was so badly worn with broken down foam (inside the cover where you couldn't see it) that it couldn't be used. And there was only an extremely basic amount of kitchen equipment - to the point where we had to buy some basic stuff, such as a tin opener!! Oh, and there was no step supplied either.
These hire vans are obviously heavily used and abused and possibly not looked after or checked over between uses by the rental firm.