Sounds like you might need to set one of these babies up..
Mine started out like yours - a few dodgy periods then quickly deteriorated into pure garbage a lot of the time.
Gazing in my crystal ball I see you..
Moaning on the VM community board
The the reps admitting that they've oversold your local bandwidth and saying they'll raise a fault with networks.
Giving you a meaningless number you can't check up on.
You asking about when the meaningless fault number is likely to be fixed
Them saying in 3 months time
(this is where I am at the moment)
Things gets foggy now but I imagine there will be slippage on that three month date - the commuinty board has plenty of examples of that.
Not sure exactly what I'll do but the first step will be a downgrade to 10Mbps - a different network so just possibly OK and if so often faster speeds that the overloaded one I'm on - plus £14 a month less.