Useful links

APA Association of Publishing Agencies
  APA is the representative body for customer magazine publishers.
  http://www.apa.co.uk/
   
ASA Advertising Standards Authority
  ASA is the independent, self-regulatory body for non-broadcast advertisements, sales promotions and direct marketing and administers the British Code of Advertising, Sales Promotion and Direct Marketing to ensure that ads are legal, decent, honest and truthful.
  http://www.asa.org.uk/asa/
   
ABC Audit Bureau of Circulation
  The circulations of more than 3,000 magazines and newspapers around the world are certified by this UK-based international company.
  http://www.abc.org.uk/
   
FIPP International Federation of the Periodical Press
  FIPP is a trade association with membership from national associations, magazine publishing companies and associate members worldwide.
  http://www.fipp.com/
   
NRS National Readership Survey
  The National Readership Survey is funded by PPA, NPA and IPA to conduct research into the readership of consumer magazines and newspapers.
  http://www.nrs.co.uk/
   
PPA
Periodical Publishers Association
  The Periodical Publishers Association is the organisation for magazine and business and professional media publishers in the U.K.
  http://www.ppa.co.uk/
   
PPA Marketing.....
Periodical Publishers Association Marketing
  Catering for advertisers, agencies and publishers, the site contains data and trends on the industry, as well as case studies and research supporting the case for advertising in consumer magazines.
  http://www.ppamarketing.net/