As far as I can make out from the photos, the Cambridge 13 are all 1984-86 Ligier JS6's, which would have all been fitted with 49cc, 9hp Derbi two-stroke engines. I think it was only later versions that had the 325cc diesel option. According to my papers, their vital statistics are; 1974mm long, 1280mm wide and 1434mm tall. Or 6ft 5" long, 4ft 2.5" wide and 4ft 8.5" tall in proper measurements.
If you can get a list of all visible reg numbers, I can advice on presence of V5's. Also, armed with said numbers I can often come up with further background history... It might also be worth poking about a bit if you can, just in case the original engines are all sat on a pallet somewhere. Also, is the Enfield bonnet anywhere? I'm itching to know what the low old thing with spoked wheel & big brake drum is in one pic and that front wing with headlight that's poking into a couple of other pics as well. Basically, do what I would & take photos of EVERYTHING everywhere!