I've put together a detailed UK postcodes map in Maproom. It includes all 3,064 four-character postcode districts in the UK.
Postcode districts are the alphanumeric identifiers used in the first part of a postcode, e.g. NW1, BN12, SO8.
The commercial map includes all the labels, but aesthetically I prefer a version without the labels. I like the cracked mosaic effect!