If you are one of the virgin mobile payg customers, then you can unlock your phone by giving a call to their call centre and ask them to give you a code. The only catch in this deal is you have to top-up your phone by £30 or more. Customer assistant will explain this to you. If you already have got balance in your account then don' t hesitate and give them a call that you need to use some other sim on the handset. They will send you a code by post within 7 days or if you can't wait that long, give them a call the nexy day after asking for code.
Hope this will help all Virgin Mobile Phones customers.