Chicken/egg?
We hire immigrants because there are not enough local skills.
Or.
There are not enough local skills because we hire immigrants.
.
If there was a true labour shortage then there would be more incentive to hire locally and train.
There might also be an incentive to improve working conditions and pay in the current zero hour seasonal minimum wage jobs.
This might, of course, cut into supermarket profits and increase the cost of the very cheap food.
The choices then would probably be to scrap the Uk farming industry and import everything or perhaps impose an import tariff to prevent the dumping of cheap food from low cost production areas on the continent.
EU migrants come here because despite working conditions and accomodation possibly being worse that they might see at home the overall package is better. Else why move? Economic slavery is probably marginally better than unemployment.
Shit! I'm sounding like a Brexiteer.