Steve.
I wish i had run my machine from my vehicle, but never thought of it. After 3 years in business, i have bought a new truckmount from Prochem in August 2005, the Blazer. This is fitted into a long wheelbase vauxhall vivaro.Less back breaking than lugging the porty down steps or up them.
Going back to the portys manufacturers, i did not like the fact that when i stripped the machine to repair or replace the wate pump, they had purposely ripped off part of the lable on the pump so you cannot know its model No and source it from anyone else but them. I repaired the solenoid myself as it had burnt out using a micro switch from a washing machine shop.
I don't know whether you have ever replaced the vac motors, or how much they charge for these, but i payed £175 from my local chemical distributor, and could have got it cheaper again from a specialised motors dealer had they not also removed the label from it as well.
The solution hoses used to cost me £15 for 2 x 7.6 mts and i would fasten my own ends on.
Dave