I have to point out that Norway and Switzerland are practically part of the EU in most fundamental senses. Norway is a member of the EEA, so it has had to adopt much EU legislation, while Swiss bilateral accords have meant that it is now basically part of the EU without any influence over what decisions are taken in Brussels which directly affect these nations.
Indeed, the EU debate is being reopened in Switzerland because joining it would at least mean some influence over EU legislation (commission, parliament, committees etc). Moreover, the EU has said that it would no longer negotiate a third round of bilateral agreements with Switzerland.
Both Norway and Switzerland are miniscule in comparison to the EU (world's biggest economy and their main trading partner) and in some way or another they HAVE to adapt their own laws every time the EU/EU leaders pass legislation affecting their economies.
Although Britain is larger than either of these two, it will also have to adapt its own laws/adopt EU ones if it desires to trade with the bloc. The argument "we can save £X if we leave the EU" is false because Britain will no longer be part of the free trade zone, its benefits, and will no longer be able to influence EU legislation or laws which will affect it directly. Every deal will have to be negotiated, tarrifs have to be contended with, native laws adapted etc.