Regarding Germany and its single main stations - Germany is a federal state with a much less centralised history than the UK. None of their cities compare to London in terms of size and concentration of rail need. Even at the main Munich station there are only 32 platforms - how many would London need in total? Destruction in WW2 and Berlin's divided history helped to keep land clear to create a major interchange at their new Hauptbahnhof. So, unless some random terrorist blows up a massive section of central London and clears some land, it's not going to happen here.