To make a statement like "These were the winners or losers of Brexit" you'd have to clone the universe at the point of the Brexit vote, change the outcome of the vote, and let this parallel universe run forward in time. Then you could compare that parallel universe to our universe and see who is better off and who not. This is, of course, not possible as far as we know and probably never will be.
Going in after some number of years and observing that certain parts of the population are better or worse off conflates a ridiculous number of things.
So, in conclusion, statements like "Brexit was bad/good for low/high income households in the UK" are always and exclusively made for political purposes. Which is OK. But let's not pretend this has anything to do with science.