Expect nearly a 50% reduction in your take home pay then!
Virgin love to tell you about the £5000 per year you will take home in additional allowances. Remember that these are provided for subsistence down route and are currently vastly reduced by the strong pound if you plan to bring any dollars home.
Probably why they didn't want you to pass the maths test!
I'd stay where you are, it's not worth paying to work for Virgin.