Anyone who owns, operates, or is effectively in charge, of a CCTV system that covers an area that is accessible to the public, is required by law to be trained and qualified to SIA standards.
This means that they have to be aware of, and abide by, the letter of the law regarding your rights to access any recordings that you may be involved in, as well as your rights under the Data Protection Act.
Breaches of these rules are a criminal matter, and if you believe they have occurred then talk to a solicitor.
Tampering with video evidence always leaves a digital imprint on the records, and a court can require any licenced operator to provide the records as evidence in a hearing.
If you are serious about these allegations then you need to get advice from a legal professional, and not, with all due respect, the unqualified members of this forum.