Brexit was presented as an opportunity for this uniquely talented nation to free itself of EU shackles and look to the wider world. This always felt like simplistic nonsense but it now looks ridiculous with the rise of nationalism (of which Brexit was a portent) and increasing calls for protectionism. Also, the salesmen for this English exceptionalist, buccaneering Britain BS have been once and for all revealed to be dilettante charlatans by the UK government”s shambolic response to Covid-19.
But, to answer your question, our mighty fishing industry might benefit. Maybe it can increase its share of national GDP above 0.1%.