The eastern european workforce were there to fill a gap like fruit picking, working in factories etc, doing jobs that the local workforce didn't want to do because they were so back breaking and badly paid
I worked in not fruit picking but a similar industry. The above is simple not true.
When I joined the industry, the core staff were working class, they had permanent full time jobs. Seasonal staff were brought in, local students in the holidays, contractors(worked for an agency that found work for them throughout the year) and anyone looking for job.
JSA was quite flexible allowing people to take on weeks of seasonal work, without it causing major disruption for weeks on end because of signing off and on, due to seasonal work.
Quite often other seasonals workers would get permanent work. Occasionally a summer student would applie for permanent work and drop out of Uni.
most permanent were put through NVQs going upto level 4.
I didn't see anything wrong with the changes that occurred at the time as things slowly changed.
The first year Eastern European workers came, they lived on site in caravans, were lovely people and hard working. (that year though no students, contractors, or opportunist were taken on)
Same the next year. The contracting agency for the local seasonals folded.
Some eastern Europeans stayed and settled down took permanent work, and rented houses and started families. most returned home at the end of the year.
20 years later the structure of the industry is completely different now, So yes when you suddenly take away the staff they rely on, there is a hole, you can't just call a local seasonal agency anymore they've all gone.
you can't get the skilled staff for the permanent full time jobs, because mostly they are home grown from original seasonal staff. Which are all now EE, so if some permanent staff go due to Brexit, and you can't bring anyone up from the seasonals either because of Brexit then yes its fucked.
and unfortunately the bottom line is, what happened to the jobs that locals use to be able to find? That is why in some areas people were upset with the unbridled immigration.