If, as free-marketeers, our Brexit-leaders believe in the laws of supply and demand, the demand is for the unskilled who’ll do the jobs most Brits won’t touch with the proverbial.
Catering, caring, car-washing, fruit-picking and even (in our case) bin-emptying will grind to a halt will unless we a) make it attractive for those who will do the jobs for the money available to come here or, b) make more money available, so natives for whom the jobs are infra dig might deign to do them.
Which will mean paying a lot more for your pizza.