Colin's channel is entertaining but it's as synthetic as TV. He has a team of people, probably has planning permission for the whole thing, and so on.
I would say it is more artistic license in the story he is saying rather being artificially synthetic.
The original bunker had to retroactively apply for planning permission: https://planning.southkesteven.gov.uk/SKDC/S16-0017/1288446....
Of course it's way more organised that it first seems, because it is sponsored after all, but he does seem rather fly-by-night o all his things.
He said he was going to do a load of other projects with that bunker (including ventilation systems) but they never happened.