In reply to jussy:
Seconded- convert your own LWB/hi top van.
The only caveat to that I'd say is that to genuinely sleep and accommodate five people requires more room than most folk on this site require, probably requiring that at least some beds can be fitted transversely (if I slept sideways in my self converted van the bed wouldn't be long enough). Commercially built campers tend to be wider than ordinary vans giving you that bit of extra room. So it is perhaps worth considering an old purpose built camper so long as you know its history- there are plenty of low mileage and little used but old campers out there which have only been used a couple of times a year so a service history/lack of rust is what you need to be looking for.
For example- the first one that came up on eebay item number 252864180061 is the sort of thing you might consider. Plenty more like it there.