Nice idea Nigel, sadly wont work/not practicle , I run a 6.5kva diesel genny in the back of my Berlingo for when I'm outside its regular range and I need a recharge, theres no hope of it actually running the van while driving, then theres the noise, I've got a boxed so called silent one and you REALLY dont want to be in the van or even near the back of it for any real length of time without ear defenders, an open frame one is even noiser
I'm not convinced about the output of that one on e-bay either, its only got 9hp engine, mine 10.5hp and it just can do 6.5kva peak, 6kva cont. I suspect that one is more like 5kva peak, 4.5kv cont.
EV's suck huge amounts of power when they are running, 60mph and the berlingo is pulling a good 100 amps, thats 16kw
even a 6kva genny isnt really going to make a dent in that I'm afraid.
Its a nice idea but unless you fit something thats going to generate 25kw then I think its not going to work
looking forward to hearing more about your Enfield