I would guess because the UK economy is worth ~£2tn. £150bn of imports raising at 20% isn't a huge impact (around 1-2% - not a huge deal in the grand schemes of things).

PS: I didn't downvote you.

That's because of the London banking. Which is now moving th Frankfurt.

fat chance, some back office operations will move (as little as possible), and the lucrative front office work will remain in London as that's where the clients are