We've got a bongo and had it converted to a campervan.
You can have a choice of side conversion (cooker, fridge, cupboards etc) along the length of the van behind the drivers side) or a rear conversion (across the back but this means cooker facing out and having to cook with rear door open). Latter obviously stops you putting a bike inside!
Main difference between the two is size of bed. Side conversion is narrower (width of a single bed) but about 7ft+ long. Rear conversion is wider bed (full width) but obviously not as long.
Beds are normally made from using existing 2 rows of rear seats which fold flat (ours were shortened but we still can carry six people) or by a specific 'rock n roll' bed which is not so safe for carrying passengers but does give you more space.
Our roof lifts up to give (a) more headroom and also (b) an extra bed space if required. We haven't tried the roof bed but it is supposed to hold a grown up couple and is much bigger at full size of the bongo (almost a double bed). If you just used the roof, you could do away with the downstairs bed and get a bike in easily I guess.
Our roof was not factory fitted (these add about £2.5 / £3k to the value of a decent solid top bongo) but rather fitted ourselves by a local specialist.
Any photos please ask.
Best place to get more info is the bongo forum -
http://www.bongofury.co.ukWe love ours - having taken it all over Europe (Croatia, Italy, Switzerland, France to name a few) on different occasions.
Having said that, we haven't used it this year due to a young baby so are thinking of selling it. Any interest?
