I was on Virgin 20mb for ages (and it was always spot on what it should be) then I upgraded to 50mb in November and it's been mint until recently.
Downloading 5.5-6mbps and uploading around 200-210 kbps.
I say recently because for the past 2 months it's been running at 30mb. Apparently there is a fault in the area with the upstream utilization. It should have been fixed by now but it hasn't yet.
To be fair though they have been refunding quite a bit each time we've had a problem. Last month they refunded me £45 off my months bill, which is basically the 50mb cost p/m so I can't complain about their service.
They do try and palm you off with some dodgy bullshit artist from Pakistan first off to try and "solve issues" etc. Just go through to disconnections instead and they'll sort you out 