What did France and Britain do? In fact nothing – they had an excuse of Hácha’s ‘invitation’ of German forces.
Only the invasion of Poland on September 1, sovereignty of which was assured also by the British government, was the last straw that forced Britain and France to action.
Some could even argue that the final end of appeasement came with the end of the so-called Sitzkrieg (also “phony war”) in spring 1940. Although the British and French declared war on Germany on 3 September 1939, their armies waited (cowardly?) behind the Maginot and Siegfried frontier fortifications. However, the warfare at sea was since September 1939 under way – when both Britain and Germany launched blockades against each other (with laying mines, sinking merchant- and battleships).

Conclusion
All in all, it seems as if all authors advocate Britain by saying that it was not prepared for the War. Although moralists could counter-argue that wars usually do not wait for all states to be absolutely ready for it, it was Britain who had to make this crucial decision. Britain would be blamed for the beginning of the world conflict. Hitler’s military attack on Czechoslovakia was perceived as a fact, as an environmental condition, rather than the breach of peace.
British response, believing that the appeasement would soothe the conflict and bring the so wanted peace (“peace at any price” - Chamberlain), having the possibility to catch up militarily , focusing on problems in areas of British vital interest, determined by domestic situation as the public opinion and the uncertainty of the support of its’ Dominions, seems from this point of view as an egocentric but rather pragmatic one.
It is very tempting to think about history in terms of ‘what if’. Some could suggest that if a firmer attitude had been taken towards Hitler he would have not risked a war. Many high-ranking German soldiers and officials maintain this option. A military plot if pushed to the wall could have as likely overthrown Hitler. If Czechoslovakia had resisted, its’ well-trained more than 30 divisions with support of mighty fortifications could have withstand for even two months. France could have decided to fulfill her obligations; USSR might have sent a few squadrons of planes to Prague. What would have done Britain then? It would be really interesting to know...
Nevertheless, some of the lessons of Munich are clear. We may learn from it that unilateralism and neutralism are in the serious times foolish, it reveals the necessity of close cooperation between threatened states, the penalty of deserting faithful allies, the dangers of discussions at the highest level without careful preparation and adequate advice, and the special danger of negotiating under the threat of immediate war. Munich was a big mistake.