Well done, I had similar 'negotiations' some years ago
I bought my Bongo from an importer who had the vehicle sorted and serviced by ADS Auto, I've used them ever since for repairs and servicing, really helpful guys and I wouldn't hesitate to recommend. They're at 200 South Liberty Lane, Bristol BS3 2TY - 0117 963 5999, I've seen the occasional Bongo for sale there too.
The only other 'localish' place I know that's been around a while is Bell Hill Motors in Norton St Philip (south of Bath) - I've been to see them for some body work I was thinking of having done but didn't use them in the end. There reputation is good as far as I can see from previous posts but I got the impression they had so much work they could pick and choose and name their price. They do definitely sell Bongos though.
Also noticed a place in Yate that looked to have about 6 Bongos recently but I don't know anything about them, I'd always assumed that it was a travelers site rather than a place to buy vehicles from although there are always bigger Motorhomes there. If you just want a nosey around then it may be worth a look.
Tintops look cooler in my opinion (better ratio of height to width) but the AFT makes the vehicle so versatile I don't think it makes sense not to get one. Definitely better for getting changed in with the roof up and you can have the kettle on for a brew whilst you do that by putting it in the roof above the front seats. If you decide to stop the night you also have the option of sleeping up there. Only downside it watching the height in multi story carparks.
Next decision is seating styles, kind of depends what you want, mine is 97 so old shape with a slight facelift (no orange strip across the back and a few other minor cosmetic changes). Before 97 the rear set of seats flip up out of the way, 97 onwards they are usually sliding bench seats. I chose to buy a model with 2 x bench seats but to be honest I think the flip up ones may have been a better bet (I'd like to have built a small camper unit and removed one of the flip up seats, facilities and 6 seats would be great. More tricky with bench seats although they do slide back and forth so if you are after that vintage, it's worth working out what you want. New models only come with bench seats (as far as I know) and it's not easy to change them.
If it's just you (or 2 of you) then I'd suggest bench seats but take out an entire row - loads more space and the remaining seats will slide right to the front for loading up or right to the back for maximum 'living space'.
I've tinkered with mine inside a bit and used it as a surf van, family camper (there are 4 of us), daily car, some pics to give you ideas (most of this is still really prototype that I never got around to making better):
Home made 'picnic' cupboard - hold essentials. Note only one bench seat (with home made drawers), the other was cluttering up the garage at the time.
Brackets secured to roof holes which I use for straps to fasten the board straight onto the roof. The bikes are on a BakRak (I dont use that for bikes anymore, I now use a Maxxx Raxx which is easier) but it was really useful for other stuff. I had a 'cushion box' from B&Q on it at one stage and it was great to hold chairs and wetsuits etc. Others have done the same so suspect a search will find some pics.
Home made roof rack ( a bit heavy as steel but does the job) - mainly used for relatively lightweight camping gear (chairs, boogie boards etc).
Currently I have all seats in but the middle ones reversed so they are facing each other. No pics of that but you'll find some on the forum as quite a popular thing to do. For a day van, just doing this and adding a table makes a cool place to chill and doesn't take long.
Hope that's useful, quite a few in and around Bristol area , don't forget to wave
Good luck searching.