I was surprised how marked the northern (particularly north western) bias was, when I worked the situation out.
The cabinet, compared to Blair's last, is slightly less Scottish and slightly more northern English. The members who left the cabinet were Blair (North East), Prescott (Yorkshire and the Humber), Reid (Scotland), Jowell (London), Armstrong (North East), Beckett (East Midlands), Hewett (East Midlands), Lord Falconer (East Midlands) and Baroness Amos (London).
Because, in that case, the Northern bias is only apparent. Can the last politician to go out the revolving door please turn the lights off?
To some extent. An example is Alan Johnson who is a Londoner, with a constituency in Hull, East Yorkshire. Shaun Woodward has a large estate in Oxfordshire (when he was a Conservative he represented the same South East region seat David Cameron now holds).
I imagine a Conservative cabinet would probably show some bias to southern and eastern England. I have not done the exercise, but I remember there was some comment about the number of Cambridgeshire and East Anglian MPs in John Major's cabinet.
Extending the analysis to where the MPs really come from would be quite difficult. In any event most of them live in London, most of the time.
Politicians who don't even have to pretend to give a damn about the people they represent...