[Kushan]

The Cat5/Cat5e thing was an issue for 50meg users as it was. It's "good enough", but there were situations where Cat5e would give a speed boost. I never seen this myself, but it was something mentioned to me during training so it must have been an issue at some point.
However, I was also told that it was the customer's own cables causing issues rather than Virgin's cables.

In any case, it's not much of an issue - computers for the last half a decade all have gigabit ethernet. If they don't, then they're too old to make the most of 100mbit+ anyway. Besides, the real use in these speeds is multiple machines running at once, so it's a bit moot.