Another key point is that, if you were able to get consent for the cable, then as you own the parking space I think you would be eligible for the grant. However, you could probably only get the grant if you had consent to run a cable over the path.
If you can't get this consent, then I suspect you may not be able to get the grant, in which case just fitting a charge point at the end of your garden and running the cable (suitably protected) across the path seems like a reasonable option. I doubt that the freeholder would be the slightest bit bothered by such temporary use, if they found out about it after the event. As long as no one complains about it then they probably wouldn't ever find out.
I'm pretty sure that there is a fair bit of stuff like this that goes on with no form of consent, anyway. Many years ago we had a neighbour (in a terraced house, with no off-road parking) who had a Heath Robinson arrangement to sling a cable over the pavement, on a sort of home made gantry set up in his front garden, so that he could warm his car up in winter. He had a fan heater set up inside the car, with a lead running to the boot, and would use this to make sure his car was nice and toasty inside before he set of for work. Everyone nearby joked about it, but he never got into any trouble with the council about it.