The problem is you're just taking a few countries where it hasn't worked and saying "see, all these countries have copy and paste electoral systems and they don't work"
But, none of those countries have the same system, none of them have the system being proposed for the UK. So it's just noise.
The problem with the Tory/Lib coalition is this country is not at all designed for coalition governments and therefore they principally do not work, if the Liberals in anyway disagreed with the Tories and pulled out of a vote, they would be paralyzing parliament.
In Scandinavia, you agree coalitions BEFORE an election and the second largest parties leader takes the role of minister of finance, the direct right hand of the PM. It's not some topsy turvy world, it's something that happens all over the place. If you don't want a direct coalition, you can have voting blocs. Again, this happens all the time.
The way you stop extremist parties is a simple % threshold.
The only other option is parties like the Lib Dems, Reform, Greens are forced to shut down and get behind two of the big tents and we go the way of America, two party system with no hangers on.
