Ossiv said: Have anyone tried if that is possible in game? To win the UK by sinking all or most convoys, without landing any troops to the UK soil?
It's not mechanically possible. Even with maximum war support loss from convoys being sunk, the UK will still have enough war support to stay in the war.
The UK will be useless with no merchant marine and easy to defeat, but you will need boots on the ground.
Now, based on things I've done to Germany, it should be possible to drop British war support below the 50% threshold by a combination of bombing, convoy raiding, and using spies to damage war support (and stability and democratic support). With a ton of effort, you should be able to coup Britain, but I don't know if that could succeed without some German troops sailing across to give Mosely a hand.