O2 have the z5 compact for £168 on o2 refresh. Take out the £25 1gb tarriff, once received request unlock then pay off the £7 x 24 device plan and cancel the airtime. Or you can purchase pay as you go like new for £179.99.
O2 also have the like new z5 for £232. To get this tariff select the 1gb £18 with £39.99 upfront and do same as above.