Just received an email off Xbox saying that silver members can buy 3 months of live and get one month free.. I know this isn't the cheapest, however is convenient buying directly from Xbox and working out at £3.75 a month isn't too bad :)
email from Xbox saying:
"sign up for a three month Xbox Live subscription and we'll give you an extra month free!"
* Offer valid 22 February 2010 5pm GMT - 8 March 2010 5pm GMT. Only available to current Xbox LIVE Silver members when upgrading to a three month subscription at £14.99 through their Xbox.com. The three month subscription will automatically be extended by one additional month for no extra charge.