But the best thing that you can do is just put those funds on localbitcoins, and sell that amount to a seller, that is very easy and if you want a wire transfer it can be made in just minutes.
I didn't knew that blockchain.info had the option to withdraw money, i mean, i thought that Coinbase was the only one who was offering this kind of alternatives to withdraw some bitcoins.
Maybe it is because the miner fees, but 5 pounds seems to be a little bit expensive (since atm's fees are aprox $3)
I'll be sure to move my Bitcoin out as soon as possible and find some sellers.
As for Blockchain allowing users to sell Bitcoin, I believe that not too long ago they made a partnership with Coinify to provide that service.