Hi bearhands,
No real idea about dealers up your way. I know there's a place outside Edinburgh called Calder Leisure who sell Steppies and do camper conversions but I know nothing about them other than what they say on their website. The seats, when folded make a a nice flat area of around 4' 6" wide by 6ft ish long. I've never slept on just the seats, preferring instead to use a double futon on top of them and that was fine for 2 people. You could also use a double airbed if you preferred. Definitely fine for an overnighter. (I think the amount of 'flatness' you can achieve depends on the seat configuration you have. The Pop-up model that I have the seats go almost totally flat - the ones in the rear are completely flat but the middle bench has a little bit of a ridge. You may be able to tell from these interior shots what i mean
http://www.buyyourcar.co.uk/used-car/ho ... 02952.aspx. The Turn-around model goes even flatter (I believe) and the middle bench also rotates so you can sit facing one another in the back like this
http://www.spectrum-imports.co.uk/photo ... G_2092.JPG. On both models you can also recline the front seats all the way back and use them with the flat middle bench to make two small singles (I suppose you might want to do this if you had stuff in the boot).
I've got to say that mine isn't great on fuel (4wd, Fielddeck camper top), averaging around 23 - 25mpg on a day to day basis and around 30 mpg on a run. I know others reckon theirs is closer to 30 mpg average. But I've never had to do anything to it in a year and a half of ownership and it is a really great vehicle to own. Definitely nice to drive than a Bongo I think.