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DirectGov and the British Monarchy have both published lists of events for the Jubilee. Alas, the events seem to mainly be a couple of weeks before you get there:
British Monarchy - Announcement of plans for the central Diamond Jubilee weekend in 2012
Public Services - The Queen's Diamond Jubilee - celebrations and events
The Official Website of the Diamond Jubilee also has more information.
However, this doesn't mean there won't be stuff to do. Indeed, if you look at the Public Services website above, there are special exhibits on at many museums and galleries, no doubt Buckingham Palace will be doing something, and several trusts are also organising events, creating new woodlands and more.