There are a number of issues coming down the line, especially if it's going to be hard Brexit. First, tariffs will be applied, although these vary from 2% to 10%, as far as I can see. Will this lead to a shrinkage in trade? Unclear. Second, if the City loses passporting, this might involve some firms moving to the EU. Unclear also. Third, loss of investment. Unclear. Fourth, slowdown in growth. Unclear.
If it's soft Brexit, all change, but seems unlikely at the moment.
So that's all very clear! The govt is hiding in plain sight, as it's difficult to talk about stuff that you don't know. It's two years at least to leaving the EU, so likely effects are guesswork.