De Beauvoir Cycle Gang Strikes Again

The central London postcodes are obviously

WC1, WC2 - West Central 1 and 2
EC1 - EC4 - East Central 1 - 4
With the WC1 and EC1 being at the very centre
Then you have W1, SE1, SW1, N1 & E1 being the neighbouring areas headed in the respective direction.

Then it becomes alphabetical
eg

N2 - East Finchley
N3 - Finchley Central
N4 - Finsbury Park
N5 - Highbury
N6 - Highate
N7 - Holloway
N8 - Hornsey
N9 - Lower Edmenton
N10 - Muswell Hill

etc etc

Mike ought to add that SW & SE restart at 11 (Battersea) & 19 (Crystal Palace) respectively. And the 'place' refers to the name of the sorting office, so even though N8 covers parts of Harringay & Crouch End as well as Hornsey, the postcode is Hornsey.