Same problem here in South London (Balham). I don't know if it is anything to do with the Discovery Bar which has just only shown on my box since installation?
From the status page on Virgin Media:
We know of 1 issue in your area
You might find that some of your apps such as iPlayer & Youtube are either a bit slow to load or Freezing/Buffering at the moment on your TiVo® service. Our engineer is working to fix the problem. Reference no: F004233744
Fix estimate 19 February 11:15 Sign in to get updates