If I get a Nokia Lumia 520, can I use my virgin sim?

I currently have an iphone 4s but I'm considering getting a Nokia Lumia 520, sim-free with no contract. I'm with Virgin on a unlimited sim which my dad pays for. Pretty good, only £15 a month. Firstly, how much will it be to unlock the Nokia and, If I do, can i use the virgin sim?
Also, is it a good phone? My biggest wants are:
A good app store and battery. My Iphone sucks.

HI you can't use your Nokia lumia 520 mobile with virgin until you unlock it… The cost to unlock your phone depends on the carrier with which it is locked. You can easily get your phone unlocked using sites like http://www.mobile-unlocker.com/nokia-lumia-520/rs1wp9/ here they are providing unlock code for all mobile models at reliable cost. You first check that whether the code is available for your country and network provider. If yes then pay for it and unlock your phone.