Macroeconomics: UK economy, IB Economics

How is Britain's trade with the EU going to be altered by Brexit? According to this article, it would seem that, in the short-term, the answer to this question is going to be "not much", as we are going to operate a relaxed policy regime for 6 months with goods being allowed to enter and tariffs being paid retrospectively.

It strikes me as a Johnsonian solution in the extreme: avoid doing anything remotely close to work prior to the event and then make it up as you go along. I wonder how stringent any checks will be, and how much potential tariff revenue the government will lose as a result of these temporary arrangement?

I can also see an awful lot of stocking up - as firms import large quantities of goods before more formal checks, and use this as a way of avoiding paying the appropriate tariffs because they can pretend that their orders have remained at normal levels. 

But then again, this is probably what the government actually wants because it will delay the time period before any post-Brexit inflation feeds through into inflation figures, and the extra profit that firms pocket probably won't go amiss either.