Look for smoke when accelerating hard (use driverside mirror). Black/grey maybe OK, blue lots, not...
Check the engine bay for completeness and neatness and the cab also, if it looks like bits are missing, choke control just left of steering wheel, frinstance, nice tidy lecy junction box at rear back of engine bay etc and engine and rear of van not covered in oil, that might be a starter for 5 points at least.
Easy start from dead cold is good (has he pre-warmed it up before you arrive?)
Must be TD, not 1.6 N/A
If its over 100,000 maybe you might want to see bills for what's been done to engine if anything.
Geachange prob won't be as good as yours, but it should select all gears of course and not jump out (lift off in 1st 2nd and 3rd to see if it stays in OK)
If it's marginal, or incomplete, I'd make big monetary allowances for that...
Russel will tell you more, I'd take his phone number with you in case questons crop up..
Owner should confirm TD or not, wll it go over 65 for instance
Expect it to be noisier and less refined than the one with yellow wheels..
Good luck!