i get my tv programmes streamed, and surf the net at the same time no problems there, infact the adsl provider i have and been with for 3/4 years, i can say is the best BB provider out there.
Ill hazard a guess that you stream most of them illegally, and if you are streaming them legally then you can do the exact same with virgin, providing you dont stream a ridic amount between 4-12, and even if you do you're only getting cut down to broadband speeds that were more than capable of streaming said quality video 2 years ago.
Im fairly sure you cant legally stream the content available on virgin's on demand service