Marmiteandjamislush
Ps I'm not a fan of apple, so may be biased.
I'm not either Marmite! 
OnIlkleyMoorBahTwat
Sim free phones with Gif Gaf type sim only contracts are usually cheaper than 24 month contracts at thirty odd quid a month - always add up how much it is going to cost you over the 24 month contract to compare costs. Obviously though, you have to pay a large lump sump upfront.
I have a sim free Samsung Galaxy SIII with a monthly £12.00 GiffGaff Goody Bag. This does everything I want, it might be nice to upgrade one day but I definitely don't need to.
This Goody Bag offers 250 UK minutes, unlimited UK texts and unlimited Internet for one month. Also free giffgaff to giffgaff calls and texts on top of that.
Presumably there are other providers who also offer similar deals.
My 19 year old DSD has an sim free Iphone 5s with the same Giff Gaff monthly £12.00 Goody Bag, she says this does everything she wants. She has never run out of minutes.
My DP has a sim locked to T-Mobile/EE with a Samsung Galaxy Mini which has a complicated system of rewards and offers and costs 35p per minute for UK calls. Giff Gaff costs 10p per minute for UK calls according to their website. I am at the moment trying to switch him over to Giff Gaff to benefit from the free calls and lower costs but am having to wait until his contract ends in August. His contract costs £33 a month. I do not think this is good value for money.
Out of interest I looked up what the Galaxy SIII costs on amazon now (as this is where I bought it from a shade under two years ago) and they have a sim free one at the moment for £200 plus £4 shipping:
www.amazon.co.uk/dp/B0080DJ6CM/ref=twister_B0080E458Q
Even the black version is only £50 more.