Yet, according to your own Brexiteer source, the UK economy was doing much better before the referendum:
- UK growth exceeded Germany growth by 2.2% between 2013 and the 2016 referendum,
- it exceeded Germany growth by only 0.5% between the 2016 referendum and 2023, despite the fact that Germany became the sick man of Europe because of the war in Ukraine.
https://facts4eu.org/news/2023_may_uk_growth_beats_no1_eu_state#