In order to get British unemployed workers to do seasonal work like fruit picking, the following five reforms would have to take place:

1. The entire benefits system would have to be radically altered to allow people to sign off and sign on again easily and without sanctions.

2. The in-work benefits system (housing benefit, tax credits, child tax credits) would have to be radically altered to allow someone who was registered at a specific address for most of the year to be able to keep their home at that address over the period during which they were temporarily housed elsewhere near the cropland/orchards.

3. Farmers would have to pay their seasonal workers enough so that doing a season's work picking fruit would be financially attractive to British workers. And would likely have to schedule their picking work into 40-hour weeks with two days off.

4. Government would have to come up with some real, solid incentives to benefit anyone who's willing tp spend a season picking fruit, besides the ability to save up a nice little packet of money.

5. Supermarkets would have to stop the practice of screwing farmers down so that supermarkets maximise profits for themselves and minimise profits for farmers, with knock-on effects on farm labourer wages.

And finally: Consumers would have to accept that if you want fresh fruit in season, hand-picked by British workers, it's going to be expensive.

More expensive than when fruit is picked by migrant workers who aren't being paid minimum wage.

As none of these reforms are at all likely, I anticipate that one of the knock-on effects of Brexit is either even more illegal immigrants working under highly adverse conditions to which government enforcers turn a blind eye because "everyone knows" we need them: or else, the complete collapse of most farming that requires seasonal picking labour; even more food imported from overseas.