How can I get the schedules of politicians?

I am trying to get a good portfolio together of political photojournalism, however, I'm at a loss when it comes to knowing where to be at what time in order to get the shots I want. David Cameron and Nick Clegg have promised a tour of the UK as a starting point for their leadership, and David Miliband has announced a tour of constituencies to ask where Labour needs to be improved. Is there a proper place to find out where politicians will be at any one time?