I'm not surprised if I'm perfectly honest, I even read in the Kent rag where migrants have been caught working, so I know it goes on still.
I don't order takeaway food, so it don't affect me, not sure I'd be happy if I run a local business though, especially with the minimum wage and employer NI killing a lot of places. I always get the impression that takeaway is a bit of a cut throat market.
At the same time who wants to do those jobs, unsocial hours for peanuts, horrible customers always complaining, all weathers especially on a scooter or bike of some description (cars obviously).
Although I'm not going to knock the guys for wanting to work, if you are happy to part with your cash to them, it is what it is.
I don't think there is an answer, there is always going to be a blackmarket, and at some point it will get called into check, and then go again. It's the way everything rolls mate, including cash in hand painters and decorators.

<tongue in cheek mate>