It looks like the Traffic Management Act 2004 means they can't park there, regardless of the drive being in use or not.
link to section 86
"(1)In a special enforcement area a vehicle must not be parked on the carriageway adjacent to a footway , cycle track or verge where?
(a)the footway, cycle track or verge has been lowered to meet the level of the carriageway for the purpose of?
(i)assisting pedestrians crossing the carriageway,
(ii)assisting cyclists entering or leaving the carriageway, or
(iii)assisting vehicles entering or leaving the carriageway across the footway, cycle track or verge ; or
(b)the carriageway has, for a purpose within paragraph (a)(i) to (iii), been raised to meet the level of the footway, cycle track or verge.
This is subject to the following exceptions..."