I have decided to go with a compressor fridge.  I intend to install this in a slightly different manner than most people install them.

Rather than putting vents in on the side of the van I am going to put a duct in that will channel the warm rising air into the shower cubicle.  This will not only keep the cubicle warm for me but speed up the drying of clothes.  I will then install a closable mushroom vent in the ceiling of the shower.

The ducting I will install will also take the excess heat from the exterior of the boiler.  All round a good solution I think.