If you're getting prices in USD, it sounds like you might be using the US shop rather than the UK one, and if that's the case, I'm guessing the transaction will get so far, and then they'll add on the VAT, and then your Bank will add on a totally unfounded 10% on top of that.

As soon as your address is input, you effectively tell them you're in the UK.  And to add further insult, the excuse the Banks use for the new bank charges is that it applies for anything that is not purchased in your own currency.  Makes no difference that we're part of Europe, they're allowed to do as they please.

The problem is that even on E-On's UK site, the prices are in Euros, not Sterling.  So that means the bank still gets to screw you for 10% on top of the already inflated total including VAT, even though you used the UK site and have paid your VAT.