That was a year after their Sonisphere appearance, and meant that they did the opposite of the 'A Matter of Life and Death' album tour where they did a UK tour in December 2006 at the end of the first part of the album touring process, then played at Download festival in June 2007 as part of the Matter of the Beast tour. They didn't follow up the Twickenham show with any other dates in 2008.
I would also like to point out that the 2006 UK dates were announced in March, nine months before the tour, and the 2011 dates were announced in November 2010, eight to nine months before the tour. If Iron Maiden were to announce more UK dates then it wouldn't follow the usual pattern that they and Live Nation have followed since at least 2006. No, it's too late for more UK dates to be announced and I suspect that Download festival will be their last UK show before the next album.