One of the most comprehensive pieces of media research in the UK is Ofcom‘s Communications Market report. The August 2008 edition has just been published.
The report provides a great amount of in-depth information on UK communications from a variety of angles, many of which are extremely relevant to marketing and public relations people alike.
Heather Yaxley has an interesting commentary here, and for those with a bit more time the key points of the research are here.
For a more succinct summary try Guardian Online or BBC Online.