This year's Henley Forum Annual Conference (it's the 20th!) takes place 05 - 06 February 2020 at the Henley Business School on the theme Collaboration for Innovation: Celebrating leading-edge practice.
To my mind, the Forum conference is the best KM conference by far, both in terms of speakers, content and interactivity. The location on the banks of the river Thames is also hard to beat.
You don't need to be a member of the Forum to attend and you can book online here. Note, if you an ex-member of the Forum there is a particularly attractive discount.