If you don't have one already then you need to pay to get one installed, it costs more than iRental and BT is more unreliable. Virgin Media has good broadband services, when they actually get them setup they rarely go down.
I've had my broadband fail about 5 times, and I got it back when it was called NTL, and everytime they have sent out an engineer the next day to fix it. The added bonus is that if you get through customer service and properly complain about something they just half your bill to shut you up. When with NTL we got a years free broadband and 50% off the next year because it took them 2 months to get our connection working. Then more recently when we threatened to switch to BT and get Sky they cut our cable and phone bills in half too. My friend had BT at one point and his connection failed up to 5 times a month, my area is crap for almost everything, its a 'black spot' for everything from broadband to digital TV, so Virgin Media while being crap is the least crap for my area.