Use bitstamp.net instead, you can transfer funds there using transferwise.com (local GBP bank transfer to transferwise and then they do the GBP -> EUR currency conversion and send the funds to bitstamp by SEPA transfer. Although you are paying two fx fees (transferwise's GBP-EUR and bitstamp's EUR-USD) this remains a highly efficient way to obtain bitcoins as both transferwise and bitstamp give you fair fx rates.
You can actually use this same setup to deposit into mtgox's polish euro bank account too, but mtgox requires account verification (upload passport and utility bill scans) before you can do that and anyway bitstamp has currently lower prices than mtgox.
Another great option for the UK at the moment is https://bitbargain.co.uk - buy person to person usually under <10min using pingit or a UK bank transfer directly to the seller's account. The prices don't seem too bad at the moment either.. £9/BTC is only ~2% higher than current mtgoxGBP ask price.