can i use a virgin mobile UK sim in a T-Mobile UK phone?

HI you can't use virgin sim in your phone until you unlock it from t-mobile network ...You can easily unlock your phone using sites like Unlock-Free.com they will generate network unlock code for some older mobile models at free of cost .Else if you want to unlock some other new model phone then visit sites like MobileUnlockSolutions.com they are providing unlock code for all mobile models at reliable cost .After unlocking your phone you can freely use it with any GSM sim ...I haven't used virgin yet now so i am not aware of their call quality for more details you can contact your network provider .