we had this issue at work (british gas) some vans are clear cut transit vivaro etc, the grey area comes in with car derived vans at the time we had transit connects, vauxhall combos, renault kangoo and citreon berlingo , basically all the same sized vans, we had an engineer caught on camera in glenrothes in a combo doing 70, the ticket was queried with fife police, the traffic inspector later dropped the charge. we then asked for clarification from them and took four vans along . the kangoo,combo and berlingo were classed as car derived but the transit connect was classed as a panel van, this was due to how the manufacturers classed them.
the company now has a blanket lower speed limit set on the fleet and governors set at 74
there is also differences in 110,s mine is a 110 hard top and the log book says 2995 kg and so is mot,d as class 4 some are plated as 3500kg and motd class 7 although i dont think theres any difference in them , i believe the ex utility company ones are plated higher.