What did the UK just dodge (temporarily)?
The IMF’s most recent World Economic Outlook has an interesting box on the subject of Brexit impacts. They analyzed several scenarios in addition to the baseline.
The simulations are shown below:
Notice that not only do each of the “no deal” scenarios imply recessions (relative to baseline), the current baseline is below the April 2016 (pre-Brexit referendum) baseline. In other words, the uncertainty associated with Brexit has already depressed economic activity in the UK.
More on estimates of the Brexit costs, see here (scenarios assuming orderly withdrawal).