Ok, thanks JimBall.
Now I'm sitting up...
When you say "To operate an unlicensed landing site within Class A airspace (all of London zone west of Vauxhall Bridge) you need to operate with CAA permission and obviously with ATC clearance."
So, permission to do so boils down to the discretion of the CAA. I take it then, the odd wealthy individual flying to the football game in his ("very unlikely to crash" machine) would be okay (subject to huge fee) but a farmer (I am not a farmer btw) wishing to operate a Jodel or similar (and not able to pay huge fee) to mind his flock would not?
This ultimately is what is driving my curiousity (perhaps I have thought about this too much!) . To what extent can the rules be waived for agreeable applicants/proposals.