I fear the point you're missing there is that if you have no tariff barriers for goods (and nothing else blocking a free-trade zone) then your Government loses considerable control over the economy anyway. It might be less obvious because there are no visible regulations 'imposed' from outside, but it loses control because it ends up at the mercy of all the businesses that can say, in effect, if you don't lower this tax rate or remove this safety standard, we'll just shift production to country X that doesn't have safety standards/high wages/etc. The EU regulations might seem unpalatable to those who wish all decisions to be made in the UK, but by making all countries follow similar standards etc., they to some extent protect against exactly that race-to-the-bottom.
In the end, you have three choices:
1. Leave the EU, but keep free trade zones outside the EU, but then that free trade naturally deprives you of your independence anyway, and risks pulling the country into a low-wage low-safety low-tax etc. economy, whether you want it or not.
2. Leave the EU and put trade barriers up. That way you keep your independence, keep more control of your economy. But the downside is the loss of free trade means less efficient production and overall living standards will fall.
3. Stay in the EU, and keep the free trade and the external regulation. That way you keep the economic benefits and higher living standards that tend to result from the free trade, and the EU regulation/harmonization protects you (albeit imperfectly) from the nightmare of large businesses playing countries off against each other - at a cost of decisions being made at the EU level. (Or of course: Leave the EU but then sign back up to most of the EU regulations so you can access the EU free market - then you just lose the ability to influence those regulations without really gaining anything)