What the cheapest SIM card i can buy to get a mobile number in london?

I have never been in london, before, but i need to get a SIM card so i can get a mobile number in london and be reached. I've seen vodafone and t mobile websites, and although they seem to sell SIM cards at 50p and free, respectively, I don't know what's bets. Besides, i need to know if there's one distributor of those companies in the heathrow airport so i can buy my SIM as soon as i get to London, any information will be appreciated.

What the cheapest SIM card i can buy to get a mobile number in london?
T-Mobile is best for texting - you can get a free SIM card from their website. Vodafone is best if you will be receiving a lot of calls from overseas and making a lot of calls and texts overseas (go for their Passport option, they also have free SIM cards available on the website).





The problem is you won't have time to get the free SIM card from the website, Also you will need to have your phone unlocked for another company's SIM card to work in your phone. I think your best bet is probably going to the Vodafone store in Heathrow Terminal 1 and picking up a SIM for about £5. Or find out from your current mobile provider who the English equivalent is - getting your phone unlocked can cost about £10-£20 so getting the wrong SIM card could prove very pricey.
Reply:i can get em for 3 quid
Reply:You don't need to buy a sim card to get a mobile number if you are going to connect with O2 network because O2 gives 2 free sim cards per person. You can order on-line at www.o2.co.uk.
Reply:O2 GENIE as has been suggested. £10 for a month and u get at least 300 free messages. mine started with 300, then went to 500 and now i get 1000.





make sure u keep some credit on there though otherwise u lose the free messages.





call charges are reasonable too.
Reply:go on o2, and get a free genie cheap that gives you special offers..i.e. anytime you top up you either get 300 texts or 200 free minutes and don't forget it's FREE!!


ONLY DOWN FALL YOU IS GOTTA PAY £10 TO ACTIVATE IT.
Reply:ORANG.BUY 10 POUNDS CREDIT AND YOU GET A FREE SIM CARD PLUS 300 TEXTS FREE.