1. Information about other people -
a) does this mean that we do not need to disclose any email content to a requester that contain reference or information to other people
b) does this mean that we do not need to disclose CCTV foootage that contains other people in it?
2. If we were to classify all documentation and electronic communication as ‘Confidential’ and/or as only “opinions held by the company” do we need to disclose any information at all. It would appear that if we can show that we have classified as “Opinions” we are not bound to share. "does not have to disclose personal data held in relation to a data subject that is in the form of an opinion given in confidence” and "In general, privileged information includes any document which is confidential”
Regarding your 1b question you can provide the email content to a requester if the information only concerns him if there are other information concerning other persons those information should be removed.
As far as CCTV goes unless you can blur the faces of the other data subjects you don’t need to disclose the images. There is also the situation where the requester could provide you with the consent of the other data subject that were caught on tape to disclose the footage (this is most likely only in theory). Be aware that if the requester is a law enforcement agency you need to comply based on your local legislation.
The “Opinions held by the Company” refer to legal opinions provided by qualified lawyer that are under “lawyer–client privilege” as for “Confidential” information you can always remove the confidential part of the document and just leave the information about the requester.