I keep seeing this mentioned on here as being a good idea when getting first mobiles for your chidlren. I've had a look on the website, but it doesn't seem to explain what it is-how is it different to a PAYG phone? Or do you have an existing phone and it's just a flat rate that you can't go over?
Giffgaff works like a PAYG phone. I top up each month.. you can choose the 'goodybag' you wish. Ie I generally top up with the £10 bag. (Free texts, free data, so many minutes of calls) However when I had DD2 I knew id be texting and calling more, I topped up to bigger £20 goody bag.
You can also just add credit like a PAYG and just top up when its finished. I find it very good for mobile data.
You basically get a SIM like joining a new network. Your phone either needs to be Unlocked or on the O2 network. Giffgaff uses the same network and the same coverage as O2 customers.... just cheaper.