The CAI (Confederation of Aerial Industries) for those who are wondering who the CAI are:-

The Confederation aims to raise standards within the industry; to represent its Members to Government, local authorities, nationalised bodies, etc; to unite the industry on its common aims.

Companies and/or individuals applying for membership have to satisfy the Board of Directors that they conduct a sound reputable business. Companies and/or individuals who have applied must also employ staff competent for the type of business being conducted.  They must also conform to any Standards or Codes of Practice adopted by the Confederation. The Confederation can investigate at any time and exam and test equipment. The Confederation also stipulates that all aerials and/or installations are guaranteed for a minimum of 12 months.