Plenty of monopolies?

Not in the UK. That's pretty well prevented under UK law.

In Spain, there's the energy sector which is a virtual monopoly due to its excessive political influence. Telecom used to be a virtual monopoly, but those days have recently seen their demise.

What else?

Big businesses collude with each other to ring prices at the expense of the consumer.

There are many areas where little or no competition exists.

Banks were doing that, but they got caught. Now they're gonna pay. Seriously, like the PPI scandal.

Let's see... Oil prices? Nope. OPEC is competing with the yanks and Russians. No more monopoly there.

Ermm... I'll lean out the window a bit. McDonalds and Burger King colluding to keep the cost of fast food burgers unaffordable? Cosmetic companies colluding to make mascara and lipstick too expensive for women?

If you believe that Companies do not collude to their commercial advantage at the expense of the consumer you are wrong.

It would make a level of sense for them to do so but equally, I can´t see how.
The most recent I´ve heard of was the hire car companies in Spain and I think before that, wasn´t Apple caught up in some kind of price scandle?
However, any company I´ve worked for has either tried setting the way or reflexed according to what a competitor might be doing.
I´ve never had the impression that they´re in cahoots with each other. Rather, they´d prefer to see each other removed from the market place.

The constructionindustry that in one way or another effects us all is rife with it.

Most tender documents include a non-collusion document. In the world of fair competition that would not be needed.

The subcontractors ring the prices to contractors, the contractors ring their prices with other contractors (cover pricing so a tender is submitted), the material suppliers ring their prices with each other and so on.

The scale may be diminished to what went on in the past but it still exists.

Demonstrably, they most certainly do. It always comes to an end, however. Usually with millions or billions in fines.

There are always a few exceptions, such as politically-extortionate Spanish energy companies.