How to unlock a phone on Virgin Mobile
Virgin Mobile currently sells all its pay monthly handsets unlocked, but some sold before July 2012 may require unlocking. Nearly all pay as you go phone on Virgin Mobile are locked to the network. Both pay as you go and pay monthly customers can unlock their phone whenever they want for £15.32. The process will take up to 30 calendar days and you'll need to give Virgin Mobile a call as there's no online form.
http://www.expertreviews.co.uk/mobil...e-and-vodafone
Not sure if you could do it cheaper via eBay or 'stani phone shop