In my view it comes down to three options :

Option 1 – European Economic Area membership (a la Norway);
The UK would have to abide by EU rules governing free movement of labour, plus EU employment regulations and directives.

Option 2- European Free Trade Association membership (a la Switzerland)
The UK would apply free movement of labour but could decide whether to keep its existing employment legislation/regulations based on EU Directives.
o Less employment regulation could mean lower costs for employers;
o Unravelling EU legislation would take time;
o The UK had gone further than the EU in some areas;
o Some regulations already offered opt outs – eg the Working Time Directive.

Option 3 – World Trade Organisation or free trade agreement
The UK could negotiate a bilateral agreement to make it simpler to trade. The UK would not be bound by EU employment regulations or the free movement of labour. Some form of immigration control would probably exist – establishing criteria for EEA migrants to come to the UK.