Nigel,
If you have good ideas, you'll always face people who want to knock you down to their level or to use you as a free of charge design studio. FWIW, you are lucky that this introduction has only cost you some $ ... others have lost six months of effort or even something they spent their whole adult life perfecting.
My advice: continue to share ideas, but stick to off-the-shelf slogans rather than directed expertise shaped for a particular client. When you get a contract, over-deliver. People soon figure out that you are a smart dude who converts cool ideas into applicable reality for a reasonable fee.
Good luck!
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1
