Quidco currently have £150 cash back for all contracts taken until Midnight Sunday.
It means you can get the latest handset (HTC Diamond) for £213.98 after the quidco payment.
Login to your quidco account and follow the Orange affilicate link.
In the Orange Shop select the HTC Diamond Phone as your chosen handset.
Select 'Show All Plans' and choose the £20 Dolphin 25 plan for 12 months.
Follow on-line forms and add the delivery option of £3.99
Total cost at the moment is £363.98 (already lower than anywhere else, plus you have free minutes and texts if need be)
Once delivered take the SIM out if you want and stick your current one in (the phone is unlocked by default)
Once Quidco has tracked and validated you can expect £150 back bringing the price to £213.98
More info on the HTC Diamond PDA -http://www.htc.com/www/product.aspx?id=46278