It seems that there are only two types of payment gateway service out there at the moment; Either that the entire cart logic is handled offsite (with something like Paypal's Standard option) or the other option being that you need to go through the certification for handling credit card numbers and doing pretty much everything yourself.

Ideally, for the project I'm working on, I'm after a bit of middle ground such that I can handle the cart on-site, and only pass over to a payment gateway (with an order amount, billing & delivery details, and order ref) for them to handle the card details, before passing back.

I'm sure that I've used e-commerce sites using this pattern before, but I cannot find any payment providers out there that offer this sort of option, so are there any? The only over requirement we have at present is that it must accept orders in Sterling.