In the terms and conditions of the kite festival consent for use of footage of the audience is written into the Terms & Conditions:
5.c: Ticket Holders consent to being photographed, filmed and sound recorded as an audience without payment, and to their image being exploited in any and all media for any purpose at any time throughout the world by the Promoters who shall own the copyright in all such recordings. If you attend the Event with a child under 16 you give the foregoing your express consent on their behalf.
Note that consent is implicit, with no instructions given for withdrawal of consent. From the ICO site:
What is valid consent?
Consent must be freely given; this means giving people genuine ongoing choice and control over how you use their data.
Consent should be obvious and require a positive action to opt in. Consent requests must be prominent, unbundled from other terms and conditions, concise and easy to understand, and user-friendly.
Consent must specifically cover the controller’s name, the purposes of the processing and the types of processing activity.
Explicit consent must be expressly confirmed in words, rather than by any other positive action.
This seems to miss most if not all of these points (note "the Promoters" are not specifically defined in that document, but is "U-Live Portfolio Ltd and any associated promoter(s) of the Event").