I ran a non-equity group and was on the other side - someone kept promising to pay but didn't, then when he damaged our prop, refused to pay for it.
He turned out to be a serial non-equity group member, taking where he could and b*gg*ring off when money was involved.
I would steer away from ever operating a non-equity group again as unless you can tie someone in to the costs of operating an aircraft you are going to be left with a handful of promises when there is a cash call.
Being a non-equity member with only a £450 deposit, anyone can walk away with minimal loss - how long have you been flying in this group? Average the deposit by the hours you have flown and then decide if you can afford to write it off.
My ex-group member walked away from a £600 deposit but owed us £900 knowing we wouldn't go through a small claims court for such a small sum