I know you get a discount for having all 3, but not sure about 2, you'd have to contact Virgin again as only they understand the way it works
I'm going from my experience when I was going to cancel TV, so would just have phone and BB, the guy I spoke to said that the minimum TV package which is more or less freeview would be £X, but my discount for having all 3 was larger than £X, so it was cheaper for me have it than not to.
saying that, that was a while ago so if I phoned today I may get different answer.