Looks like http://www.ovivomobile.com/ overstretched themselves with one off payment free services and the promise of continuing them. It was never going to be sustainable without good marketing revenue coming in and they probably outgrew that as they were popular on places like HotUKDeals.
Make sure to go get you PAC if you want to keep your number!
If your looking for a new phone with contract then check out TopCashback and Quidco as they tend to have good cash-back offers (not guarantied but i've usually not had any issues, just long waits). I got my S4 on release with £150 cash back and a 12 month contract (£50pm) from Quidco last year and i'm ready for the S5 if I decide to go that way this year. It cost about the same as buying the phone outright at the time so essentially a free contract!
If you don't need a phone and want good sim only contracts then I recommend Tesco mobile (earn double club card points on your bills if thats still the same) as they have good 1 month contract prices and the best customer care i've dealt with. (Runs on the O2 network.
Virgin Mobile are also cheap but their customer service is pants. Runs on the TMobile / EE network.
If I want a 4G sim only tariff then I think i'm likely to go with Tesco mobile at the end of April. Let me know your thoughts in the comments section below.