For those who believe the market will fix it: Well paid drivers no longer exist. The last time he has seen a local work as truck driver was in mid-2000 and meanwhile salaries have dropped to ~€700 and less therefore only some Eastern Europeans can justify that working as a driver still makes sense for them. There is not much wiggle room left in terms of just paying better salaries - even smaller freight-forwarders are asking themselves whether it continues to go there (at least for now).
He is also not happy about having historically taken care of UK freight business and that he should just roll with it. He says all the customs/declaration headache with the UK is now not different than being in charge of shipping to Uzbekistan or Russia, and he can't see profits for them in the UK market only risks which especially are a bitter pill for smaller freight-forwarders.
What makes it worse is that UK customers have a high level of expectations of services. Their service industry has always been put on a pedestal especially when comparing themselves to France/Germany/etc, ... people expect cheap, fast and highly tailored to the customer. That was already hard before, and it's going to become impossible now to satisfy the expectations. As an example pre-Brexit, he had a truck go there on Monday and it was supposed to return by the next morning with a full load (booked for the way back). Now the same trucks return empty and also are stuck frequently, sometimes a whole week because even locals don't understand the paperwork. And truckers had enough of pissing into bottles too. It's a huge risk for UK businesses when the costs of the supply chain become hard to predict.
But why don't they just warehouse more stock? They have like everyone today a JIT supply-chain and there isn't any storage to stock up. These warehouses would literally have to be built.