Just to clarify - there are different laws that can restrict drone flying.
As you say, in terms of airspace the CAA regulations apply (eg NFZs around airports, prisons, other restricted areas eg central London). These are relatively easy to follow by using the NATS app or dronescene website.
Then there are bylaws that restrict activity on land. Certain bodies including councils can pass laws the prohibit use of drones. That’s the case with the NT where they have byelaws that they believe apply to drone use.
Then there are PSPO (Public Spaces Protection Orders) that can restrict “anti-social” activities for a limited period of time. I’ve started another thread about those:
Can anyone think of any others?
If none of these apply then there is no law stopping you from operating.
I guess a separate question is whether you need explicit permission. I would say on public land is no.
Public land is land where you can go and do whatever you want as long as you’re not breaking laws. You don’t need specific permission for every thing you do.
That’s why asking for permission is the wrong way to go about it.
It’s arguable different if you’re on privately owned land. The grey area is things like foot-paths where there is public access but you may be on private land. That’s for another thread!
(I wrote this at the same time as your answer above hence the overlap. Looks like we’re on the same page)