The German's rule Europe, they sell a lot of product here, as do the French and Italian's, not much would change, it would take 2 years to officially leave, a lot would be sorted in that time, it is in every countries interest to keep selling goods and services to each other.
We can not cope with the influx of migrants, the Schools and Education system, the NHS, Jobs and wages, all will become worse for the country if we can't control the numbers coming in, a points system is the only way to solve it, never going to happen if we stay in the EU.