Its never reality until proven by events, and UK economists, the Bank of England, and the CBI etc. all have a long track record of being consistently wrong in their forecasts.
People wanting to know the future after Brexit would do better to look at the tea leaves in the bottom of their cup, or reading their horoscope, than listening to these biased muppets.
Never forget that the CBI campaigned for Britain to join the ERM, exchange rate mechanism, which was a massive disaster for the national economy and destroyed countless businesses.
Why economic forecasting has always been a flawed science
The CBI and the EU