In the UK you have several methods.
Blockchain.info has "Faster Payments". The daily limit isn't too high though ("New users are limited to a maximum purchase of £100 per 7 days and a maximum single transaction size of £100.")
- https://blockchain.info/wallet/deposit-bank-transfer
Then there's BitBargain:
- https://bitbargain.co.uk/buy
You can also send cash (GBP) in the mail to Bitcoin Nordic (in Denmark):
- http://www.BitcoinNordic.com
For larger amounts you can send an International wire transfer to an exchange (e.g., Mt. Gox, or Bitcoin-24.com, etc.)
One approach that is recommended is to use a currency conversion service to exchange your GBPs to EUR and then send the EUR to an exchange. The conversion services would be TransferWise and CurrencyFair. Then withdraw to an exchange like BITSTAMP.net.
- http://transferwise.com
- http://www.BITSTAMP.net
For smaller amounts, you can buy a UKash voucher and redeem that at:
- http://mercabit.eu
- http://www.VirWoX.com
- http://www.BitcoinNordic.com (through a CashU account)
And there are many many local traders in the UK, buying and selling frequently. Here's for London:
- https://localbitcoins.com/postal_code/UK/london/
And there are individuals who trade frequently. Here are a couple:
BTC for sale for cash in Central London BTC --> GBP Pounds Sterling £££ [Tenakha]
- https://bitcointalksearch.org/topic/26-btc-4-sale-4-cash-in-central-london-uk-btc-part-coins-too-01-05-etc-147320
Buying Bitcoins in bulk (UK) [AlexNeto]
- https://bitcointalksearch.org/topic/buying-bitcoins-in-bulk-uk-130949
A fairly comprehensive list of exchange methods is on the Bitcoin.it wiki:
- http://en.bitcoin.it/wiki/Buying_bitcoins