Imports
From reading leaked govt plans, it seems goods lorries won't be allowed to board ferries at Dover unless they are either empty - only going to collect imports from Calais - or have all the correct paperwork
The govt has a priority list for imports:
fresh food, meds & med devices, chemicals for water treatment, components for nuclear power stations
Their plans are to limit outgoing lorries if need be, to avoid either Dover or Calais becoming logjammed and imports being hindered.
So, unless there is are real cockups, imports to the UK should be ok, particularly essential ones,
even if some prices may rise later in the shops
Hopefully stockpiles won't even be needed, but they are reassuring to have, just in case.
UK Exports
This is the real problem:
exports are predicted to be greatly reduced, to the EU at least and possibly to some non-EU countries
My own (v large German) firm has been cutting UK firms out of its supply chain as much as possible, in anticipation
and I know most other German firms have been through a similar process of Brexit-prepping.
The serious cumulative effects will probably only show up after 6 months or so, e.g. in the balance of payments deficit
Veteran Leave campaigner RNorth is pessimistic on what being a 3rd country means for Uk exports:
http://www.eureferendum.com/blogview.aspx?blogno=87314
Whereas a UK enterprise can at the moment ship goods to EU Member States without formalities,
after Brexit they will find that their goods come under customs supervision when they enter the EU,
and can only be released for circulation by an importer, who must be an entity established (and resident) in the European Union.
This change has scarcely, if at all, been discussed in the UK
but
the change to requiring goods to be placed in charge of an EU-resident importer represents a major barrier to trade, and an active disincentive to EU buyers.
For instance, while currently a UK exporter to the EU retains legal responsibility for standards conformity, post-Brexit the importer becomes liable, with significant cost and legal implications.
.....
for the 20 percent or so of products where there are no EU harmonised standards, and mutual recognition of standards falls away,
UK enterprises will suddenly find themselves having to conform with a raft of local standards that many of them didn't even know existed.
And without that knowledge, they are hardly in a position to prepare.
........
http://www.eureferendum.com/blogview.aspx?blogno=86804
…
It is that, more than anything, which keeps the system working
– the fact that it is populated by people on all sides of the fence who know the rules, know what they are doing and are used to working with each other.
Now, take a day-one scenario where the UK, literally overnight, becomes a third country.
As far as officials in EU Member States go, in the absence of a deal between the UK and the EU, the UK will suddenly cease to exist.
The UK as an EU Member State, accessible on all the EU databases, will no longer be there.
And inclusion on third country databases is not automatic – nor uniform in respect of different sectors and products.
…
One presumes that a company marketing nuts and bolts for general engineering use will be able to market their goods in the EU.
But if they are intended for use in vehicles, and (especially) in aviation, export may not be permitted.
Vigilant border officials will have to check loads to ascertain the intended use of multi-use parts.
Any number of manufactured goods, which require third party certification, will also have to be intercepted and rejected,
and it goes without saying that
animals and foods of animal origin will not be permitted entry.
Even the pallets on which goods are shipped may be rejected if they have not undergone the correct timber treatment.
What we are dealing with here, therefore, is potential chaos.
Thousands of vehicles each day, crossing over to EU states will have to be checked,
and possibly thousands returned to the UK until shippers get used to the new rules, and know what to avoid