I popped in today and was impressed so committed to a 12 month £15 a month contract with all of those. Got home and in a location where my O2 sim displayed one bar of GPRS I get three bars of 3G and it's actually usable, unlike the O2 contract.
It took an absolute age to cancel my contract, they attempted to say for £11 I get 100MB, unlimited calls and texts and they'll give me a voucher for £150 if I agree to a 24 month contract which basically gives me 14 months free. I then explained the Three contract I had got and they said it was bad value for money, so I asked how much I could get a 4G O2 contract for, which they turned round and said £26 a month for 4G 1GB and unlimited texts. No question that Three is the best value for money.
Been with O2 for 4 years, so they're sad to see me go, but I can't justify paying so much for so little when Three give me all of the above features for more than £10 less than my current monthly fee.
Gee was it not obvious to them that you were on an old tariff with unlimited data for a reason. Why would they even think this would be an acceptable alternative.
Anyway I think you've made a good choice. I'll probably be signing up to the same tariff next week.