My advice would be that if you can move back do so. Support are clueless and just deploy the bullet pointed script when you ring, they even logged in to change my wireless channel last night despite me telling them I use an ethernet cable.
Virgin's network is clearly over subscribed country wide and the contention at peak times is just tortuous, moving to Virgin from BT Infinity 2 a couple of months ago was one of the worst decisions I've ever made and if I could undo it I would in a heartbeat.
I suspect that severely aggressive traffic management policies / tools are having to be deployed to balance the load and that is only adding to the poor experience we are all having.
Left, gave me a excuse that the network will be upgraded in may.. proper planning that is, let's install cable into a new area, get as many suckers as possible, 9/10 won't notice that we haven't the bandwidth for them..