First of all the reason for the UK not allowing the merger is completely absurd and based on a false premise which is most likely based on not understanding the field they are regulating.
Regulation based on speculation about the future means that regulators can simply just make up reasons. Thats akin to when kings could just make up reason for their ruling. We were supposed to move away from that so that rule of law was the base.
Second, the fact that the UK can kill a deal like this is wildly problematic and unfortunately not the first time. They did the same with Facebook and Giphy where it made no sense either. It's immature and they obviously aren't understanding the field they regulate. Talk about undermining the growth of society.
Lastly I see a lot of people saying exits is not a good thing and shouldn't be the purpose. But the fact is that a healthy M&A culture is good for startups as that will encourage investors. Once you start killing the ability for exits by introducing such unquantifiable into the settings you are making investors more nervous of spending their money and much more risk averse.
Sad.