Car making a noise, garage can't find anything wrong. What would you do?

I wasn't charged. But someone above suggested I take it to somewhere that offers MOT testing for a diagnostic test. And I replied saying I'm not going to pay to have it tested when its under warranty.

Up to about £17,000, ideally 4x4 or AWD if its going to be an SUV.

Being ignorant about the result of Euro 6 restrictions is far from not knowing anything.
The Euro 3 or 4 engines didn't have such problem having even lower nominal power and FIRE Euro 3 and Euro 6 is almost the same engine (the only significant difference is in the cylinder head's shape and ECU software)
Then it appears that the design is not efficient enough to fulfill the Euro 6 regulation without limiting engine's power.
VW was unable to fulfill the regulation as well, but went another way around and ignored it, for this reason they must now pay large fines, but from driver's perspective that is the more practical option. The Euro 6 is simply at the very edge of traditional engine designs.

Surprisingly, the FIRE engine can make to 360 k miles without capital renovation, that is impossible for some VW engines.

Not necessarily. The plastic part is responsible only for the looks, and for safety of pedestrian, so it should be soft.
The strong part is the tin beam under the plastic cover.
The other thing is correct. Panda II (type 169) was technically the same as the 500, produced in the same factory and it was almost 2x cheaper.

Every manufacturer sometimes sells a "bad luck" car, it happens, correct. The point is that most of Fiats are too simple, even to say, too primitive to be unreliable, while VW is far from it's 90ties quality.

If this was true, then the car should has already been succesfuly repaired 2 times, and it hasn't.
Mechanics and factory services can be unjust and terribly incompetent, sometimes they can't even screw the wheels on properly.
There are lots of incompetent people in any profession.

Of course you're right on the principles, but I doubt if buying a new car will help you save money more efficiently than a simple test.

I think the principle here is take it to ANOTHER dealer rather than the same one.

OP, have you tried looking at forums aimed specifically at your model of car? If there are any particular common faults for that car you'll find them there, and the members will also be more familiar with the car.

If you read my reply, you'll see it has been to a different dealer. They did something different but it's still making the noise. They told me to monitor it.

Yup, as I said I've done more reading since and it seems to be a Golf suspension thing. I was thinking about changing it towards the end of the year, but I'll probably do it sooner rather than later as VW can't seem to sort the problem.