Would a rollator with bigger wheels help?
Is the driveway still to be used by vehicles?
A lot is going to depend on how big/uneven the cobbles are.
If you need to then you could put down a strip of sand or gravel to give an even surface 'bed' and then cover that with non-slip access matting.
You would probably need permission from the council/English Heritage if it's listed, but as it would all be removable and wouldn't damage the existing cobbles, you'd probably get it.
Maybe try contacting suppliers of matting for events to get their advice.
I'm thinking this sort of stuff, which may go straight on the cobbles without a bed of sand/gravel:
https://www.groundtrax.com/pedestrian-walkways/
Here's another supplier of rubber matting:
https://rubbermattinguk.co.uk/en/shop/
There are plenty of others, just google for 'event eatting'. (tip also try 'conveyor belt matting' you may find some second hand stuff cheap).