Joomla, Virtuemart and ABPro booking system

Hi all, I had someone create a bit of code that will redirect a user from the virtuemart registration page back to the previous page once they submit the registration form, however it doesn't work very well and now the site runs VERY slow once a user is logged in. The first thing I need is for someone to fix this issue. The reason I need the virtuemart registration page to redirect back to last visited page is becouse I am using it as a registration form for ABPro (an online booking system) that won't allow a user to make a booking until they register to the site or login, again this doesn't work very well and I need this to be ingerated better. To see what I am on about visit and test my site at [login to view URL] and try to make a booking!