Sure, but those are relatively small potatoes.
And if a single person does it a lot, then the tax authorities can easily examine their spending and prove that they are spending more than they are officially earning. And then they can apply punitive measures.
The cold hard fact is, the EU has more to gain by increasing trade with Russia, Ukraine, Turkey and BRICS than with the UK.
These countries have more resources, strategic locations and younger populations than the UK.