If you are struggling with memory limits and I find this happens a lot with WP Ecommerce (great plugin though). Aside from increasing the memory limit you should also increase the Apache limit which I havent seen mentioned in any posts on the subject.
Simply add this to you .htaccess file...
It works a treat. At this point (and moderators feel free to remove this part if inappropriate...but they deserve the cred), I would like to thank Heart Internet for their support they got back to me really fast with that answer and they dont limit memory if you have a reseller package.
I hope that will be of use to others.