I did earlier use the term "legally grey" and I think I was right to do so.
A fairly senior manager at the CAA told me a while ago in conversation "if you can't afford the answer, don't ask the question".
I'd suggest that so long as what's going on is (a) safe, and (b) not outright illegal, asking for a definitive answer from the Gnomes of Gatwick would be a very bad move indeed since the odds are that instead of contentedly looking the other way, they'll be forced to say "NO".
Kolibear - if clubs don't make the money to run from their rental rates, they'll make it from runway, hangerage and membership rates. You'll still pay them ! If you want cheap flying, go to a true non-commercial club and operate there in a true members-run syndicate, but be prepared for the inevitable club politics.
G