If there is absolutely no way anyone from the CAA can possibly see your 'advert', you're not (by definition) advertising. If they can, you are. And you're already caught into the bargain... Does that make sense?
Interpretations of the ANO as cited by Don D Cake:
a) Pretty straight forward.
b) You take one passenger, you the pilot must pay at least half. Take two and you must pay at least a third, etc.
c) You can stick an ad up on your flying club notice board, but not in the church hall or in the local paper. You can take your kids up, but any other passengers must be members of the club - Most clubs get round this by offering a day membership (which also means that your passengers are insured). Some don't even charge for this day membership...
d) You mustn't be on the flying club's payroll.
In my experience, it makes sod all difference anyway, as when it comes to coughing up 20 quid towards a flight, your passengers are the ones who claim they're skint. Begging the question, what the hell have they been spending all THEIR money on....
TMC