I'd hazard a guess and presume they mean that should you be offered a position, you would be required to convert to a UK issued EASA licence if you don't have one already. While I don't want to get into why they ask this, I will say the majority of airlines ask the same, for example RYR ask for Irish, EJ/BA/VAA all ask for UK.....What I would say is, it'd be unreasonable with that in mind that people convert their licence from a non UK issued one just so they can tick that box when applying for VAA- and potentially jeopardise their position with their current airline, as well as spending time on money on a licence conversion they most likely won't need if unsuccessful with Virgin...
Just curios
VJW why you think applying for a UK issued EASA would jeapodise their current position with their employer? All that is required is listed on the CAA portal. If there are no current UK TREs in their company they would have to pay externally for an LST if the triple or 78 were not on their pre existing JAR licence.
The requirement for a UK issued EASA License is a Part.FCL.TRTO requirement now. I believe it is all in CAP 804.