The Allies were certainly NOT cowards!! there was also a matter of the strategy that the allies used. we were still living by the rules of trench warfare of the 1914-18 war, you only have to remember the Maginot line to understand that!
The Germans knew what it was like to be on the receiving end of a tank, and adapted the tanks principles for a more modern mobile war.
As trackend rightly said, none of the allies wanted the war, and didnt think another one would be possible so soon after the first. People had hoped that the right lessons had been learned the first time around!
Chamberlains "piece of Paper" bought this country time to re-arm its airforce though still using outdated tactics.