Try emailing USAT first to confirm cost and shipping to uk? Cheaper than a phone call and no worries about time difference etc.
On the bottom of the parts list page it does say you can fax/email/mail your parts order and method of payment, although I certainly wouldn't include card details in an email. You never know, they might even be able to take Paypal?
Perhaps there's a US based GSC member who could act as intermediary?