GiffGaff is the most fantastic network with the best tariff rates available on the market.
This is great for you folks out there who need lots of minuites and text but dont want to be obliged to a contract.
You can simply use there sim card as a top up phone or a 28 day rolling contract
These sim cards will work in unlocked phones or even 02 network phones.
Once you recieve the sim please visit official giffgaff website to activate : www.giffgaff.com