In a previous job I worked on a site which had to meet gov UK guidelines despite not strictly being directly hosted on gov.uk, and early in production every video was re-recorded / re-produced with sign language interpretation included to meet guidelines.

They took accessibility incredibly seriously.

I don't recall running across video on gov.uk sites -- and offhand, can't think of any case where it would have been desirable.

They specifically try to steer clear of video content. It's less accessible, worse for people scanning for information, worse for people on slow connections or mobile data connections, and can become outdated whilst also being much harder to update.

They try to avoid video because it's data heavy and difficult to update. Though when I applied for a Civil Service job the videos had a signed version and a transcript.