With a UK debit card you can do this:
Simply sign up to transferwise:
http://transferwise.com/u/f0bdOpen bitstamp (or another exchange that takes a SEPA deposit) in another tab and login
Click SEPA deposit on bitstamps deposit page to get payment/banking information
Go back to your transferwise page and input the details from bitstamp by pressing the "make a payment" button.
Upload your funds to transferwise by debit card or bank transfer and when they get payment, they will then send it on to bitstamp as a SEPA payment.
24-72 hours later your bitstamp account should be credited and ready to buy bitcoin