netrg: Not really but thanks anyway
I've written (well 97% finished) a new web site for my self that has a built in shopping cart and links to WorldPay (users can choose monthly, quarterly, annual etc..), I'm just having a bit of trouble with the passing some of the hidden variables back and forth (well not some much as trouble - but finding the time! seems as if I'm juggling a million plates at the moment).
I was considering ModernBill ( or something similar) as a service for both myself and possible future 'resellers'. It looks promising, and if it intergrates into Enism or Plesk then even better!