There are two issues to deal with here.
Once the Buggy is attached to the car it becomes a trailer & the GVW (Gross Vehicle Weight) of any trailer has to be less than 750Kgs over that & it has to have brakes that work in conjunction with the brakes of the towing vehicle. Mary's/Lola's GVW was declared as 720Kg's for this express purpose however MattBlack's was registered as 800Kg's so if you are going to use this route then at SVA time be aware.
The second issue is for a vehicle to towed on an A-frame it has to be registered, taxed, tested & insured. It also must be disabled as in broken down & being moved to a place of repair.
So theoretically you can never use an A-frame or Towing dolly to take your Buggy round on Edit:- That should read an unregistered, out of MOT or out of Tax Buggy. Having said that, both mine & Matt's were taken to SVA on a dolly & then both taken to the DVLA without any comments from authorities. I also have used dolly's for many many years with no trouble at all from any Police, however there is always a risk.
Alan...