The rest of the world is a far bigger market than the small profit EU one, and the EU is the only continental market that isn’t growing.
As part of the EU, Britain was forbidden to enter into any trade agreement with any non EU nation of market. They couldn’t make agreements with India and Australia because Italy objected.
The British economy will outstrip the crumbling remainders the EU. Open trade always outgrows over regulated socialist trade.
The biggest markets are the EU and the US. They cut themselves off from the EU and it’s unlikely that the US Congress will ratify free trade agreements anytime soon.
But the UK is now free to strike trade deals with individual countries in Africa and Asia. These trade deals will create a much bigger uproar because it involves countries that pay low wages, polute the environment, etc. More Brits will lose jobs.