There's something in the 'vehicles for sale' section that might fit your requirements other than being able to part ex your car. Nothing to do with me. VW t6, 55k miles, and under budget.
I have a converted 2015 VW T5.1, returns about 40mpg average in our use. We have aircon, night heater, pop top, hob and grill etc. Ours doesn't have a fridge, but we use an Igloo 'powered coolbox' which hasn't struggled to chill to, and maintain, the contents at 4C. We've not used the hob in the van yet; we tend to use a separate camping stove and cook outside if the weather's good, or in the porch area of the awning if it's less good.
We really enjoy the van and use it loads. Just the van sometimes, or van with airbeam awning depending on our plans for the stay. From parking up, to having the awning pitched, bed made and ready to head off into whatever town we're near is about an hour. About 1hr30 to pack down, including the awning. The 'footprint' of the van is probably about the same as a Range Rover Sport, so it's really not as big as it may seem, I think the height makes it look deceptively large.
A good friend of ours has a slightly later T6, and his is currently up for sale after 2 years of ownership as he feels it's not big enough, so I think the advice of 'go and have a look at some', and maybe hire one is probably good.
That said, we didn't hire one, and we wouldn't swap it.