Thanks all the same, the more I can learn on the subject the better. Having heard back from FoxyCart it sounds as though the debit card support is still several months away, however I’m starting to think that Google Checkout could fill in the gaps. The impression I’m getting is that it would be relatively straightforward to use the JSON cart object to generate a ‘Checkout with Google’ button on the cart page in addition to the main FoxyCart Checkout button. Google Checkout has full support for UK debit cards and their rates aren’t bad at all. I could then inject a note at the bottom of the cart stating that debit cards cards are currently only supported via Google Checkout. As FoxyCart is JS-dependant anyway I can see no harm in the GCO button being the same.
I don’t think that this route would lose any customers as a fair number of larger, established sites are now offering GCO as a payment option, so I don’t think it would look at all unprofessional. I was afraid that Google would make the process awkward for users without Google accounts but having tested it they actually present a pretty standard checkout form, with the exception of a couple of password fields so that the user can create an account at the same time.
My real concern with RomanCart is that it appears to insist on you using romancart.com/cart.asp for the checkout URL, which I suspect will set off alarm bells for some users. At least with FoxyCart and can set up secure.mydomain.com, albeit for an extra fee.