Xbox.com are doing a promo where you can get One Month of Xbox Live Gold for £1. You can do it six times thus giving you 6 months Xbox Live Gold for £6.
Go here - http://www.xbox.com/en-US/live/hulu-plus/jack-links
Make sure your logged into your Xbox Live Account and select "Go Gold Today!"
Follow the steps and enjoy your cheap Gold!
mr.mean.1975 figured out that to fix the "Please enter a valid credit card number" error you have to re-enter your personal details on the accounts page and make sure they're the same as the card's billing details.
Call on 020 7365 9792 or 0800 587 1102 to cancel auto-renew
For those saying they're safe from auto-renewal because your card expires before the renewal comes up, you aren't. You still need to cancel or you'll end up billed regardless of your card's expiration date.
Everyone should also keep an eye on their bank statements to see they're not charged extra for attempts to purchase that ended in an error as someone suggested they had been earlier.