Which mobile network provider sells the cheapest sim cards?

Just the sim card basicaly, without any phone or anything. And also, if you know how much they are. Thankyou!

Which mobile network provider sells the cheapest sim cards?
You can get free ones from O2. Go on the website www.O2.co.uk and it will tell you how to apply you can get up to four sim cards for free.
Reply:o2 usually give them away do a search for free o2 sim cards. you can usually request up to four. i have four on the way now, keep one and sell the others for a few quid each. you now get 500 free texts a month if you spend £10 a month
Reply:o2 are vey good at offering free sims on the internet.or you can use vodafone.who charge only a couple of pounds and give you free calls and texts depending on how much you use your phone.
Reply:You can get one free from mobile world when you top up £10. Also gives good rates to other networks %26amp; international rates are excellent. You can buy on line or from carphone warehouse
Reply:You can get free ones from O2. Go on the website www.O2.co.uk and it will tell you how to apply you can get up to four sim cards for free.
Reply:I came across an advertisement very recently online from 02. They were giving away FIVE FREE SIM CARDS!!!!! I applied and a week later my brand new free sim cards arrived!!!! check out the website!!!
Reply:T-Mobile were giving away free sim cards instore as long as you put on a minimum of £5 top up. Think this is something they are doing until end of the month.