I don't think it will be too bad. Everything will be marginally worse, but not profoundly so. An extra day for deliveries, some disruption at the borders. A little extra cost on goods, slightly less fresh produce, and some short term pain.
Paying for 50,000 new paper-pushers (customs agents) illustrates the inefficiency and pointlessness of it. What is the payback we get? Its not less bureaucrats, as the UK has to have all these new age
nts, and new posts in government now - regulators, trade negotiators, beefed-up customs, with plenty of consultants on hand of course. Scara can stop paying the minimum wage (doubtful anyway) and use toxins in manufacturing (though this is cloaked in mystery). And lest I forget we will finally feel sovereign - at last! I don't know about you but I never felt free until brexit