Appeasement of Germany proved beneficial to Britain because it

allowed Britain extra time to build up its armed forces.

prevented the devastation of another world war.

gave Britain extra time to urge the US to join the war.

prevented Germany from unifying with Italy.

It's beneficial for Britain because: it allowed Britain extra time to build up its armed forces.

Appeasement refers to the act to avoid conflict by initiating mediation in order to achieve a certain common grown.

Even though in the end the appeasement was refused by Germany, it's still give the ally more time to prepare their troops for upcoming wars.