I pay £25 a month contract, I got the iPhone 4 free with it, and got 20% off for working in local government it's the equivalent of a £31 a month contract. DH got a military discount contract from £20 to £15 a month but the phone was naff, he'll be upgrading to an iPhone next time, we wouldn't pay more than £30 a month each although I think we would both like the iPhone 5 next time so will need to either compromise that amount or be willing to pay towards the phone I think.
(I don't even know my allowances lol, it's enough!)