I will say this. Virgin is great if you live in an area that isn't over-subscribed. Sadly, it appears that there are many areas that are. Go take a look at their customer forums and search for your postcode to see if there are any customer-reported issues. You'll soon find out.
I've had mine for coming on 4 years now. On each of the packages I've been on - 10mb, 20mb and 30mb I have always generally received a bandwidth equal to or greater than the advertised speed. Just pray nothing goes wrong though, because when it comes to anatomy, VM don't know their rectum from their funny bone.