They sound naïve. However what was the harm in their attempt? If they had been successful and had WW II been avoided, the world would have been far better off. Also not sure their efforts did not have some effect. The war would have ended with a British defeat if Hitler had not stopped the German army from completing the defeat and capture of the British BEF at Dunkirk. Some historians speculated that Hitler, perhaps influenced by these “amateur spies” thought he could enter into a mutually beneficial peace with these types of British leaders if he showed mercy and allowed the British army to withdraw. Also Rudolph Hess made that famous solo flight to Scotland. Was it his intent or impression that he could make a peace deal after being influenced by those amateur spies? Believe there is more to the story.
These “amateur spies” may have confused the German leadership. Hitler lost his best chance for victory when he pulled the German army back at Dunkirk. Historians have arrived at no consensus as to his reasons. If they had been capyured or killed,Britain would have sued for peace.
The evacuated were pretty much limited to taking their rifles to Britain.
The Allied artillery and tanks had to be destroyed and left behind in France.
I don't think the War Cabinet would have sued for peace even if this army had been lost. After evacuation, they were pretty useless for months while they refitted. The Germans still had the problem of how to get their army across the Channel - one they never solved.