All he had to do was to not force Czechoslovakia to surrender and he didn't need military presence in Czechoslovakia, deploying troops to France might have been enough. Czechoslovakia had mobilized 1 million man strong army, which would have been able to hold Germans for a considerable time. Not to mention he might have been able to get Poland to join.
Also I am not sure about which Churchill's plan to protect Poland you are talking as by the time Churchill became a PM, Poland was conquered and Germany was just starting attack on France.
Genocidal civil war when?