Another suggestion Tom, if you haven't already watched George Clarkes Amazing Spaces, it might be worth doing on one of the re-run services. There's a few camper conversions on there amongst other things (caravans with sofa-baths etc) and even a Granada hearse camper conversion.
The back end would be pretty similar to yours in terms of original layout at least and a few of those episodes might give you a few more space saving ideas.
https://simkl.com/tv/32230/george-cl...n-5/episode-4/
I know a few people have already turned "normal" 740 estates into campers, think there's a section on here, i'll look later.
