Hi Painter,
Don't know if this helps, but my mate works for British Gas (in Scotland). He tells me you can't go that far wrong with their ex-works vans. Most have speed limiters fitted at 60mph, so you know they won't have been thrashed within an inch of their life (or maximum speed limit at least). My understanding is that utility company vehicles are very well serviced - 2 or 3 times a year regardless of whether neccessary or not - (although this doesn't seem to stop them providing a cr*p service for their broadband repairs

!!) and all parts are replaced before or as soon as they are needed, so there should be a nice stack of paperwork to go with them.
From what i've been advised, the lower the mileage the better, as this can sometimes determine whether its been used around town or on more rural runs (more likely to be driven hard in the latter case).
I'm in a similar box to yourself in that i'm looking at ex-utility vehicles, but older (transit SWB around year 2000 model - which won't have speed limiters fitted!), so I may be taking more of a gamble.
The best thing is (utilities or otherwise) there are masses of connects and transits to choose from, so getting a decent one at the sort of price and age you are looking at shouldn't be too difficult at all.
Personally, i'm applying my car buying experience onto the van's - bodywork condition says a lot, as does mileage, and history speaks volumes (cared ownership etc) and even more so on a private vehicle!
All the best and hope this info helps,
Cheers,
Ben