"Are we talking about North England MPs who were parachuted into safe constituencies from the South East"?

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.