Acas (Advisory, Conciliation and Arbitration Service - as listed by gov.co.uk for 'Workplace bullying and harassment') have information, guidance, resources and both an online and telephone helpline.
They cover both employers and employees:
Acas helpline Telephone: 0300 123 1100
Textphone: 18001 0300 123 1100 Monday to Friday, 8am to 6pm
Online helpline - https://www.acas.org.uk/index.aspx?articleid=4489