questions on bigger wheels and tyres

hi all

i've got a long wheel based camper (a 3L model)
it's currently got some nice, but quite tatty 15" alloys on it.
i've looked inot getting them refurbished, and it seems that i can buy a new set for not much more than the cost of refurbishment (which seems to be about £80 per wheel where i'm located in surrey)

so, the question is, has anyone gone to 16" or 17" rims and tyres, and if so, what did you buy, where from and how much did you have to pay.

also, did anyone know what off-set the hiace imports run, and what load rating the tyres need to be please?

many thanks
nick