The press self-regulators, the Independent Press Standards Organisation (IPSO) and the Independent Monitor for the Press (IMPRESS) each have a clear process for making complaints regarding the publications they regulate. Information about IPSO's complaints process is available here: https://www.ipso.co.uk/make-a-complaint/. Information about IMPRESS's complaints process is available here: http://www.impress.press/complaints/.
Ofcom's process for complaints covers content on television, radio and on demand programme services. The Broadcasting code includes rules designed to protect viewers and listeners from harm and offence – such as what can be screened on TV before the 9pm watershed. Other areas of the Broadcasting Code address issues such as impartiality and accuracy, sponsorship and commercial references as well as fairness and privacy. Information about Ofcom's complaints process is available here https://www.ofcom.org.uk/tv-radio-and-on-demand/how-to-report-a-complaint
In addition, Government expects social media providers to have robust process in place and act promptly when abuse is reported. The UK has strict laws governing such content, which apply equally online and offline.