Recording of the mot

Basic answer is dashcam footage could be published later (social media) to identify you without your knowledge or consent. (Unhappy punter for example when you fail the vehicle so posts the video on the net & names you and/or the bisiness.)

Under data protection you have certain rights to control how any such images are used.

Your bosses should take a lesson on their responsibilities for Data Protection.

The MOT Testing Guide
Requirements for Authorisation D
Issue Date June 2020 53
conduct of the test
c) unobstructed, safe and easy access from the site entrance to the building entrance
d) adequate off-road parking
e) a clearly identified weatherproof public waiting room or area from which the whole
test can be directly observed without interruption, except for road testing (room for 2
seated people is considered sufficient)
• mirror or camera relayed images may be acceptable if all parts of the test
can be clearly observed as it would from an enclosed viewing area with
window. Consideration should be given to the quality of image produced by
the equipment used including during variable light conditions. The use of
recording equipment (CCTV) is unacceptable
• the observation room or area should be identified by a notice and floor
markings if applicable. There should also be a notice in reception indicating
the presence of a viewing area.

I just open the bonnet, all they can see is the colour of their own bonnet, that works for me, unless like said if the dashcams in the drivers view I very carefully remove it prior to the test.

The legalities I'm not sure about here, but the Test Station cannot use CCTV type equipment for recording, but the presenters vehicle is nothing to do with the Test Station. The vehicles CCTV system shuts off when the ignition is switched off if wired correctly, hence only have the ignition on for those parts of the test as required, then leave the ignition off.