West London in general is the most expensive.
1. W8, Kensington, £1,873,866.
2. SW7, Knightsbridge, £1,430,863.
3. SW3, Chelsea, £1,425,385.
4. W11, Notting Hill, £1,302,763.
5. SW10, West Brompton, £1,140,593.
6. NW3, Hampstead, £1,022,748.
7. SW1, Westminster, £1,010,228.
8. W1, West End, £987,191.
9. GU25, Virginia Water,£968,009.
10. SW13, Barnes, £958,871.
Yes it is and east is generally the cheapest.