MP political diversity.
Browsing on the Internet I found a cluster diagram on Public Whip which spatially displays MPs political locations with respect to how they vote, and this is done for the 1997, 2001, and 2005 parliments.
Below is the diagram for the 2005 parliment. A red dot represents a labour MP, blue for conservative, etc. If two MPs always voted the same way then their dots would be on the same point. Thus the greater the distance between the two MPs, the more different they are.