10707 Postepay, VISA and Paypal
Given the snaglets of paying ENEL, TI and the like with UK based credit cards, I recently trawled up this page which is all about a pre-paid credit card issued by the Italian Post Office. The Italian is pretty simple, and it might be worth ploughing your way through.
Poste Italiane are really being quite innovative with their products, and this Postepay card can be linked with your Paypal account. Paypal is also pretty innovative, and (if this payment method appeals to you) you can recharge your Postepay card via your Paypal account. Thus you can feed your Paypal account via your UK credit card, bung some money onto the Postepay card, and pay ENEL. All online, as far as I can make out. In addition, anybody in Italy who owes you money can nip into the PO and credit your Postepay card (which you can then move into your UK credit card account via Paypal). Nifty stuff.
I have absolutely no idea what sort of charges or exchange rates would be involved, but 'in extremis' it could be a goer. Even ex-extremis it could be cheaper than running an Italian non resident bank account!
[url=http://www.poste.it/bancoposta/cartedipagamento/postepay.shtml]Poste Italiane - Postepay[/url]
It gets higher tech still - get a load of this!