Link
The report came out in September and uses information gathered from March-May 2013. Of particular interest here is the section on ebooks. I've only skimmed it so far so others may find other tidbits, but I found interesting that they estimate 1% of the (presumably UK) internet population download ebooks illegally.
They've also listed where respondents get their ebooks from, which gives the side effect of providing some info on ebook seller market shares in the UK (though I'm not certain exactly how accurate it is since it's respondents versus hard data, and it's not really shares since respondents could choose multiple answers). These estimates also include sites that can be used to acquire ebooks illegally, which give a very interesting view on the situation.
Here are the percentages of respondents who used the top services:
79% - Kindle (Amazon)
9% - ibookstore (Apple)
8% - Google search engine
6% - ebooks.com
6% - Google Play
5% - Email
5% - Kobo (WH Smith)
4% - Facebook
3% - (a particular grey site)
3% - Waterstones
(in grey) 7% - Peer-to-peer (net)
(in grey) 2% - Cyberlockers (net)
The last two are coloured differently presumably as they are conglomerates of various options that can be used for illegal acquisition, so at least 7% who download ebooks use those kind of sites.