If I might be so bold as to stick my 2p in... I am aware of a flight school who got into trouble a couple of years ago with the CAA for the 'T&G at a licenced airfield' method, when their own base's licence changed. The complaint came from another school at the licenced airfield used I believe. Happily the matter was resolved without charges being brought.
'Fraid I don't know any more than that, or I would have written it.