There's tons of people in email jobs who are just clamouring to get up at 6am and gut fish! /s
Something not really addressed in all of this is that a lot of the people whinging about British jobs and so on, especially in high-Brexit areas, are actually themselves retirees.
https://www.bbc.co.uk/news/magazine-36619342 "Of the 30 areas with the most elderly people, 27 voted leave".
Now, they're often living in economically depressed areas. I've seen Blackpool and Lowestoft (the sad little marker of the UK's easterly point, right next to a gas terminal). But you can't give them their jobs back, because they're not working any more. It's nostalgia.
I'm going to keep hammering the question of "why should people move from lucrative, comfortable email jobs to harder, less lucrative factory jobs, or, god help them, fishing?"
The UK is actually at ""full employment"" (NAIRU): https://obr.uk/box/the-equilibrium-unemployment-rate/ - that is, economists believe it cannot go lower without causing inflation, as shortages mean you can't hire people without having to offer more wages to poach them from other jobs.
(Another conundrum: people want higher wages without higher prices. How are you going to do the arithmetic on that?)