Regarding filming and photography, this is the Met's advice to officers which I would expect to be echoed nationally
From
Photography advice - Metropolitan Police Service
Guidelines for MPS staff on dealing with media reporters, press photographers and television crews
There is nothing preventing officers asking questions of an individual who appears to be taking photographs of someone who is or has been a member of Her Majesty’s Forces (HMF), Intelligence Services or a constable so long as this is being done for a lawful purpose and is not being done in a way that prevents, dissuades or inhibits the individual from doing something which is not unlawful.
Contact with photographers, reporters and television crews is a regular occurrence for many officers and staff. The media influences our reputation so it's crucial to maintain good working relations with its members, even in difficult circumstances.
Following these guidelines means both media and police can fulfill their duties without hindering each other.
Creating vantage points
When areas are cordoned off following an incident, creating a vantage point, if possible, where members of the media at the scene can see police activity, can help them do their job without interfering with a police operation. However, media may still report from areas accessible to the general public.
Identifying the media
Genuine members of the media carry identification, for instance the UK Press Card, which they will present on request.
The press and the public
If someone distressed or bereaved asks the police to stop the media recording them, the request can be passed on to the media, but not enforced.
Access to incident scenes
The Senior Investigating Officer is in charge of granting members of the media access to incident scenes. In the early stages of investigation, evidence gathering and forensic retrieval take priority over media access, but, where appropriate, access should be allowed as soon as is practicable.
Other parts deal with the terrorism excuse, which suggests that the use of supposed powers in the past have actually been illegal