Thanks for your post @Exile_Nige, and a very warm welcome to you!
Not exactly a Virgin Mobile question as such, but I can confirm that if the phone has been purchased from Virgin Media, the handset will already be unlocked and therefore any sim card would work in the device.
I'd also advise roaming is switched on, before you leave the UK, and that you ensure the sim is fully activated in the UK, before you travel
Kindest regards,
David_Bn