If you are paying Microsoft £4.99 a month for your Xbox Live account or you are buying an Xbox Live pre paid card every 3 months, STOP!
With this pre paid card you can save a whole lot of money, if you're paying Microsoft £4.99 a month, then you can save £25 a year. If you're buying a card every 3 months you can save alot more. At this new price of play.com cutting £5 off, it would be mad not to pick one up since they won't be doing it forever.
The card comes in a proper Xbox 360 case, but you can't use it as a spare game case. (See my review for Microsoft 2100 Points)
To use it: sign into Xbox Live, go to the Xbox Live Marketplace blade, click on "Redeem Code" scratch off the silver foil at the back with a coin, enter the 25 character code, and done. Sign out of Xbox Live and sign back in for the changes to take effect.
You will get an e-mail at your registered address confirming your Gold subscription, too. However, if you want to check on the 360 itself when your membership expries, and what have you. Go to the Xbox Live Marketplace blade, then "Account Management" then "Memberships" it tells you all the information there.
While I am here reviewing something about Xbox Live - I'm not sure if many people know this but, you can register up to 3 accounts on your 360 which give you a months free trial of Xbox Live Gold. I thought I'd just mention this incase people are coming to the end of their membership, and aren't ready to renew yet. Obviously you'll have to make a new Gamertag, and such. But if you just want soemthing that's tempory, or more than one person uses your 360 but you, there you have it. I'd say it's more of a tempory thing really, to be honest incase something happens to your main account, like what happened to mine (got stolen)
Great buy from play.com once again, if you're in need to renew your Live membership this is the one you should go for, and at a discounted price of £5 off you can't go wrong.
Credit to play.com once again, thank you.
To answer Freddo 111's question: you can't play U.S games on a British 360.
You can register a U.S Xbox Live account (when registering the Windows Live ID pick United States as the country) however, in order to use the Gold service, and you can't just buy a UK pre paid card. I heard you get banned if you attempt to register a UK bought pre paid card. Not sure what the situation is if you pay via credit card though. As for content; it should work but I don't know 100% could try it, and give it a shot. If you haven't registered any other accounts on your 360, if you look above you can register up to 3 accounts on your 360. The first 3 get a months trial of Xbox Live Gold for free. Hope this helped, and good luck.