We recently developed an XML API for connecting to the HSBC bank in the UK for OSCommerce based systems which is free for everyone to download, update and even improve. I forgot to post a link to it so here it is and it should help everyone who wants to use them get up to speed pretty quickly
Download: http://addons.oscommerce.com/info/5585
Support Forum: http://forums.oscommerce.com/index.php?showtopic=284821