Two professional bodies for the marketing sector:
Chartered Institute of Marketing (CIM) – Worldwide professional marketing body. Defines the marketing standards that operate in the UK. Provides membership, qualifications and training to marketing professionals
Direct Marketing Association (DMA) – Trade association in the marketing and communications sector. Aims to protect consumers and raise industry standards. Members include agencies, list brokers and mailing houses, as well as blue-chip corporations
Take a look, get more informed about the sector you are interested in.