ACORN - CACI Ltd.
http://acorn.caci.co.uk/
CACI have developed ACORN,  a geo-demographic postcode classification tool used to help businesses get information about, and understand, their consumers. ACORN classifies 1.9 million UK post codes and generates 287 different lifestyle variables that a business can use to profile its customers. It classifies the entire UK population into 5 categories, 17 Groups and 56 Types. In addition to this, CACI have developed ‘Financial ACORN’, a tool which divides the British population up in to 11 groups according to financial sophistication and a further 49 groups according to their financial behaviour. ACORN was the first and is still one of the most powerful consumer targeting tools. It enables marketers to fully understand the kind of people buying their goods and services or shopping in their stores. By analysing key census variables and lifestyle characteristics, it provides precise information and an in-depth understanding of the different types of consumers in every part of the country.

Kantar Media – Consumer and Audience Targeting
http://www.kantarmedia-tgigb.com/
Established in 1969, the Target Group Index (TGI) is a continuous survey which measures product usership, media exposure, and attitudes, in order to describe as accurately as possible the characteristics of target groups of consumers and the potential strategies that enable subscribers to communicate with those audiences. TGI service enables advertisers, agencies, media owners, and publishers to identify, target, and reach their key consumer audiences. TGI survey provides essential consumer insights, building effective consumer understanding and audience profiling for media planning and buying. The data is trusted by the world’s most influential publishers, media owners, agencies, trading desks, and advertisers. The survey operates in almost 70 markets worldwide.

Euromonitor
http://www.euromonitor.com
Euromonitor International offers quality international market intelligence on industries, countries, and consumers. They have more than 30 years of experience publishing market reports, business reference books, online information systems, and bespoke consulting projects.

Experian Marketing Services – MOSAIC
http://www.experian.co.uk/marketing-services/products/mosaic-uk.html
Experian Marketing Services is a proven expert in helping global and local brands maximise profitability, strengthen advocacy, and extend customer loyalty through actionable consumer insights, precision targeting, enhanced data quality, and cross-channel marketing. Mosaic is Experian’s flagship consumer classification for today’s multi-channel world, providing a deep view of UK consumers’ characteristics and lifestyles. It seeks to provide unique consumer clarification based on in-depth demographic data.

National Statistics
http://www.ons.gov.uk/ons/guide-method/classifications/current-standard-classifications/standard-industrial-classification/index.html
This link will take you to the website of the UK Standard Industrial Classification of Economic Activities (SIC codes), a tool for categorising businesses and other organizations by the type of economic activities they carry out.