SecPay and NetBanx are a couple of UK specific ones I have also dealt with. I am currently sticking with Paypal. They are not the most competitive but I think their anti-fraud measures and data they hold must be the most secure in the world.

I have just signed up to their full merchant service called website payments pro. This costs £20 per month! But the rates come down to 3% and lower. It is a full online merchant service with online terminals etc.

I will let you know how I get on.