How to prevent users from skipping payment and gaining access to the site

Hi Guys

I'm in real need of help on this

I have my site which is running the membership plugin. It is an auction site and I wish to have it set up in such a way that only paying members can bid, buy and sell.

The auction theme I am using allows logged in members to buy and sell.

When using the signup process the membership plugin jumps in and asks for payment etc. but if the user clicks away without making payment they are able to log in.
Where as the membership plugin allows me to block the URL of creating an auction it but the bidding and buying feature is javascript.
So if you are logged in you can bid.

Does anyone have a genius idea where I can prevent members from clicking away from the payment process during membership?

If they dont pay I dont want them to have access to bid.
However I do want non members to see site activity to draw them in.

Hope someone can help.

Kind Regards
Mark