The UK User Group also takes advantage of the space here on the Tableau Community site which I think you've joined. The UK group leaders usually post event notifications in that spot as well as on LinkedIn. Lastly, we always post something on the events page for each User Group meeting and there is an option to follow that via RSS.
Hope that helps. Let me know if I can answer any other questions.
I'm with the Atlanta user group and a week or two before each meeting we ask Tableau to send out an email to those within the Atlanta area. You might want to ask the admins of the UK user group to include you on their distribution list.