Just a guess here, but the UK decision to make porn "opt in" beginning next year and to filter porn has something to do with how aggressively Kobo and WHSmith is dealing with this now. When they have finished with it, and the titles that are not an issue are back up, they may mirror what has been done in the UK elsewhere.
There is discussion about doing the same thing in Canada, btw. Background info here:
http://www.huffingtonpost.ca/2013/07...n_3636481.html