Revenge porn is the publication of explicit material portraying someone who has not consented to the image or video to be shared. It is an offence to disclose a "private sexual photograph or film" without the consent of the person depicted in the content, and with the intent to cause them distress.
A person found guilty of this offence will face a fine or even imprisonment.
If the circumstances do not fit the above offence, i.e. there is no intent to cause distress but the photo/video is, for example, on one of the social networking websites, you could speak to the administrator of the internet site who may remove the material. Otherwise, you would need to obtain a restraining order from the courts to order the removal of the material. You should seek advice from the Citizens Advice or a solicitor about this matter before going ahead.
With regards to showing photo/video footage of yourself without your permission and there is no intent to cause distress, if you are over 18, the footage needs to be classed as grossly offensive or indecent, obscene or menacing character (the legal threshold of which is quite high and would not normally cover what could be classed as merely offensive).
If you are under 18 then the footage needs to be classed as indecent before the police can become involved.