Hi Martin. I have one of these going spare if you’re interested?
My brother in law has a carpet/flooring shop, and he very kindly laid a pukka vinyl floor in my shed. He also sorted me some squares of ply with carpet glued to one side. So for each bike, I put the centre stand on the section of ply, carpet downwards, and the bikes slide across the floor pretty easily. Hence the dolly is going spare!
Let me know if you’re interested in the dolly. I'm not a million miles from you, so could easily drop it off. Cheers