My brother and me found the best deal ever with giffgaff: using the O2 network and for only 10GBP a month, you will get 500 minutes of calling other networks or landlines (I barely can't finish, it's been 3 weeks already and I still have 183 minutes remaining). Unlimited text and the best...1 GB internet!! And you get all of this for only 10GBP!
Calls and text between giffgaff are, of course, completely free. Even if you finish your monthly allowance you can still phone another giffgaff for free during 3 months! Is it amazing? ;)
I want to share this little, still unknow jewel with you. It's your call, but not other company will offer you a better deal "pay as you go".Not many people knows about Giffgaff yet in the UK. You can use it all around the country, including Northern Ireland (but not the Republic of Ireland, as it is a different country)
More Info you can get it from here (plus 5GBP extra credit!):