Ah, this one again!
So, DCA have heard from a few cavers over the last couple of months with varying experiences. I think Nige Atkins popped in for a chat and all was well with parking there as it was in the past, but there have been reports of a couple of issues more recently when cavers went in to ask permission. Mind you, I know a team who went last week with no issues at all. DCA would probably officially suggest you make alternative parking plans in the absence of a clear, repeated permission.
Personally speaking, I've not had any problems ever. I park at the far end on the 'dirty' verge bit, keeping clear of the hotel windows and 'nicer' parking. I've not had any problems, but have never asked for permission. Never been covert though, so it can't be that bad. Crack on, say sorry if accosted and let me/DCA know if you have any issues.