Same problem here I'm on 150 mb package been getting around 1-2 mb since last night about 10ish. In Edinburgh area 11. Phoned this morning about 10:00 and went through the usual reboot your router your pc unplug replug ethernet cable etc etc . Didnt work so they reported to Networks and also booked an engineer visit for Monday. Got an txt reply from Virgin at about 12:00 this morning cancelling engineer visit , saying Network problems will advise when resolved - no update so far and still running at 1.5 mb.
I'm on 200 but lucky to get 20 after 3pm during the week and rarely above 10 once you get to 8pm.
Right now, I am getting between 2-8 down and 0.5-2 up, with pings ranging from 250ms to 780ms.
The usual reboots of routers, internal kit not making any difference this time.
Unfortunately the super hub is in my daughter's bedroom and I don't want to wake her, so can't make the support call now (that asks for the usual "turn it off and wait x minutes, connect a device directly to it, no we are not making any config changes, oh ... it magically works better") ... so we'll have to see how poor it is in the morning.
If VM is 100% at fault, utilization (over subscribing) is their problem, then make a formal complaint with VM, after 8 weeks if its not resolved take it to CISAS, follow my simple guide to make it easier.
You can, if you provide enough evidence to CISAS you can get up to, if not more than 50% of your BB costs.
Hit them in their pocket not yours.
( Guide taken from Bartman007 so credit goes to him )