I'm need a module to interface Drupal 5 with HSBC Secure ePayments (UK).

Probably for eCommerce, but I'd also consider Ubercart.

I'm envisaging a Card Payment Interface (CPI) solution (where orders are taken on our website, but the customer will enter their card payments details on the HSBC website) as opposed to an Application Programmable Interface (API) solution (where orders and card payments details are completed on our website). But API may be OK too.

More details: http://www.hsbc.co.uk/1/2/business/cards-payments/secure-epayments