AlanM, your comments are quite interesting, particularly that the CAA has clearly seen you give certain clearances and hasn't seen fit to complain about them. That to me is a pretty big endorsement, though I realise, of course, that you are not personally (as ATC) endorsing anything. I have read your comments on the other thread
I know what kind of clearances people tend to get (singles less far west) and I realise it isn't your job to police. I also completely understand that it is the captain's decision to accept or decline your clearance. What I am trying to do is put together enough information to make that decision. Look at it this way - how can I know if there are places to land if I can't fly over it and have a look?! Maybe I need to rent a twin with good single engine performance for a one off trip.
FFF, I'm not too sure about your first point. No, ATC don't know the glide performance of my plane, but I bet the CAA would take the trouble to find it out if they want to prosecute me for breaking the ANO.
If your comment in 3 (not just a clear bit of the built up area but actually outside it) then surely the Thames and the reservoir are out? In which case the whole thing is out. In which case, how come the CAA have not done anything about it when they audit AlanM?