I have been on the giff gaff mobile network for about 18 months and have never looked back! It is a PAYG network so no contracts but they offer monthly Goodybags starting at just £5 which are great value for money. The £5 package gives you 300 texts, 60 minutes and 20MB internet which is ideal for light users (such as my mum!) and you also get free texts and calls to other giff gaff numbers. Additionally, if anyone calls you from a non giff gaff number for more than one minute, your minutes allowance gets topped up immediately! I usually opt for the £10 a month bag which gives me 500 mins, 1GB internet and unlimited texts which is more than sufficient, especially as my mum and hubby are both on giffgaff too so are free to contact. For heavier users the £18 bag gives 2000 mins with unlimited texts and internet! The community support forum is great and if you order free sims for friends and family, you get credit on your own account. Giff gaff piggybacks on the O2 network so reception is excellent.
I have used giff gaff and the past and I do think they are excellent. It's easy to use and the referral system is very generous. I prefer PAYG and it is affordable as long as you choose the right goody bag. I also bought a sim just for my tablet which was the best deal available as I only needed it where I had no wi-fi, so I didn't want a contract, and giff gaff does a monthly goody bag for that.
I think that there are a lot of people who think that this network isn't as good as others because of the fact that it is so much cheaper, but I don't think that it is fair, because in my experience the network is excellent. I have never been without a signal, and always have enough calls and texts to see me through until the next month. I am only a light user at the moment because I tend to do a lot of my communication online, as it is easier and quicker to talk to the people who I am interested in. If you want to save money, then this is definitely the network to go with. Other people always spend way too much - because the other networks charge too much by far!