If you really wanted to deal in GBP you could use
https://bitcoin-central.net but the transfers would work out more expensive than taking the transferwise/SEPA/EUR deposit and SEPA/EUR straight to your bank account for withdrawal route
So it would be easier to send my BTC to MT Gox then convert to Eur, then send that to Transferwise/SEPA/EUR deposit and then SEPA/EUR to my bank account? Such a long process haha!