Some very interesting stats have been released by a company called Ellecoya, who optimise broadband networks for operators. They relate to North America, but I can't imagine the picture would be radically different in the UK.
The statistics cover the relative approximate proportions of different types of web traffic, as deduced by analysing the usage data of about a million subscribers:
HTTP - 46 percent P2P - 37 percent Newsgroups - 9 percent Non-HTTP video streaming - 3 percent Gaming - 2 percent VoIP - 1 percent
Very interesting. VoIP remains lower than gaming, a lot of things remain lower than newsgroups (still!), but more importantly HTTP is a fair bit higher than P2P - for the first time in four years.
It would be interesting to see the same study done on UK traffic...