It's odd looking at North/South (forgeting London for a moement, that's different) houses arround £100k and £1million.
I reckon comparable houses in Reading and Middlesbrough are about 3-4x difference in price. But once you get over £300k the difference shrinks raplidly. £1million in the Chilterns is proabbly only 25% cheaper on the Yorkshire Moors.
Seems like wherever you are there's a consistent ammount of consistently rich people. It's the average to poor demographic that fluctuates.