Personally, I wouldn't touch 'em.
What's on a Mac van? You've got Britool/Expert. A great make once, now trashed by various owners and now simply a brand name attached to just about the crappiest tools out there. There's no shortage of crappy tools, so who buy's 'em from the Mac Van, especially in the U.K. where you can get better tools for less money from every Halfords!
Then you have Facom. Again, great tools once, but the same machine is concentrating it's energies on trashing Facom too, and a line that was once predominantly top quality European tools is now having poorer quality Taiwanese imitations substituted at every opportunity. I suspect some Facom sells from the truck in the U.S. where it's a bit of a novelty and the Mac truck is the predominant source, but again, I can get Facom from any number of sources in the U.K. Online, high street, and even eBay! Oh, and all of those are cheaper than the Mac van too, so no sales there either!
Finally, you have the actual Mac line. Great. Decent tools, USA made, and even it's own following! Except that already the 'saleable' Mac tools are only accounting for about a third of your stock. Now what have you got? Ratchets, sure, very nice! A breaker bar, yes, but not actually made by Mac, so it doesn't match. A sliding T, ah no, long discontinued! Sockets, yes, but only some are Mac USA. Mac 'edge' are Taiwanese as are all the hex and torx. Might as well go back to Halfords for anything other than the US made Ratchets, Sockets and wrenches, and I doubt there's a living to be made there!
Personally, if I wanted a tool truck for the U.K. market I'd start my own.
No need to stick to one brand, or even one quality level (maybe have 'top end' and 'shop grade') Get screwdrivers from PB Swiss and maybe Wiha. Pliers from Knipex or VBW. Hammers from Thorex, Punches from Eclipse or Priory, Wrenches Sockets and accessories from Stahlwille, Hazet, KoKen or King ****! You get the idea.
You can offer tools better than most of the stuff on the Mac van but at lower cost, without paying any money for a franchise, and with the ability to call wherever you like! If the business doesn't work you can sell the van for what you paid and the tools likewise on eBay! If the idea works you could start selling your own franchise!
I have an independent tool van where I am, and even though he's done it wrong (it's full of Taiwan ****) and most folks don't buy anything, he still survives!