I think the UK is going to be fine. People are flexible and there is no comparison point of what would have happened if there wasn't a brexit. And EU isn't doing so well either.
We'll
survive. But the point is brexit was meant to make things
better. Since 2016 the pound has already been devalued. £100 in Euros, 22nd June 2016 = 130.5 Euros. £100 in Euros, January 2020 = 112.6 Euros.
This deal means that we have swapped free access for what we import (goods), for no access for what we export (services). The main issue has always been the UKs (really, England's) inability to accept that we're not a superpower any more. Britain's view is that it somehow is the EU's equal. It is not; it is a bit-player. The sheer economic power of the EU will mean that in practice the EU will do what it wants and the UK will have to lump it. Same when we go begging for deals with other large countries. For example, we can secure a relatively quick trade deal with the US, so long as we bend over. And we will.
The biggest long term loss is international power and influence. The UK, along with France and Germany, was one of the big three EU nations with the power to dictate the direction of the bloc, and the right to opt out of conditions that other member states were expected to comply with as a requirement for membership.
While a member of the EU, the UK could also veto EU proposals that they didn't like.
When, in the perhaps distant future, the UK rejoins the EU, it will do so as a member state with power more like that of Italy or Spain than France or Germany.
And as an independent nation outside the EU, the UK's ability to negotiate treaties and trade agreements with any other nation in the world has taken a massive blow, not least by their having demonstrated their untrustworthiness and willingness to consider unilaterally breaking international law when that is seen in Westminster as expedient.
Brexit, like the Suez crisis, has revealed to the world how powerless the UK has become; And like the Suez crisis, that harm to the nation's international standing and reputation is irreversible.
Oh, and in the short term, food and other essentials will become scarce, and expensive.
All of which seems to more than offset any advantages that might arise from hearing fewer Polish accents in the high street.