Obtaining cctv

Any person whose image has been recorded has a right to be given, on request, a copy of the information recorded. In giving a person a copy of their data, the data controller may provide a still/series of still pictures, a tape or a disk with relevant images.

If you are hoping to identify another person or vehicle involved in an incident a request under GDOR would be of very limited use as other people's images/data would need to be obscured before the data is released as you have no right to their information, only your own.