Peter,
I really feel for you, I had the same nightmare, I sent out letters, banged doors, etc. I produced my BASC membership and like you got nowhere.
Then I got a small paddock........Turned out to belong to one of the biggest landowners in the area....hey presto 10,000s of acres......snowballed to the point that I now have to turn down permission.
Keep it up, dont get totaly demoralised be polite, courteous when being knocked back as I am now shooting on land i was initially turned down on.
I am so looking forward to the post in the new year that says 'bloody hell its a yes!!