Surveys and market researchers and other researchers split the country a number of different ways:
Too long to list here in detail, but use search engine of your choice to research the following:
1. The Government Offices for the Regions (there are now nine standard regions in England, plus Wales). Postcodes do not fit exactly into these.
2. TV areas � basically these are the old ITV regions of about 20 years ago and are still the way ITV does its local news programmes. Popular with market researchers, because of the way TV advertising is still sold. Postcodes do not fit exactly here, either.
3. Postcodes. These comprise postcode areas (the first two letters of the postcode), district (the whole of the first part of the postcode) and sector (the first part, plus the initial figure at the start of the second bit of the postcode)
4. The ACORN and MOSAIC systems use postcodes (use your search engine to research these again); ACORN is run by a firm called CACI; MOSAIC is run by Experian. Both the above systems classify areas by sociological profile (they can distinguish between "old money" and "new money" for example, or, at the other end of the scale, distinguish between different sorts of deprived area).
Hope this helps...