Thanks for all the advice. The location is secure. A local company with green credentials is kindly allowing me to locate them inside one of their high security areas. Got to do risk assessments, and make sure groundspeople don't stumble into them though. Groundspeople are ok with them there, so no issues.
My car is a 4x4 pickup, so very suitable for bees, rough going, carrying stuff around etc. So ok on that count.
I'll add in some local storage for tools, supers etc. Good idea to save repeat visits.
Ditto for the ammo box for hot smoker. I've got a couple of smokers, so leaving one on site would be good.
The hives are currently sitting on paving slabs. Need to either take these, or think of another way to level them up. I like the idea of the metal adjustable feet ... maybe I can come up with something suitable. And yes, I saw mole activity. My cat keeps the moles away from my garden.
Looking forward to putting them there! It'll be a bit less convenient than in the back garden, but I'll keep that space clear for nucs and swarms until I move them on.