You added probably the most important piece of information in a comment. You are in the UK.
The UK government has a website about this:
It quite clearly states:
You usually will not own the intellectual property for something you
created as part of your work while you were employed by someone else.
Simply put, NO; it is not OK for you to use the images.
You own no rights to the images/videos you create as an employee; the employer owns them. And there is nothing in your contract about it because it is settled law in the UK.
The Copyright, Designs, and Patents Act 1988 (https://www.legislation.gov.uk/ukpga/1988/48/contents)
11 First ownership of ...