Chamberlain never willingly moved a finger to stop Germany until he was basically forced to by few remaining sane Brits, and even then British declaration of war meant horse shit, they only did so because they were forced by papers. Britain (and France, for that matter) would leave Poland under Soviet-Nazi ocuppation pretty happily, so you can say that the actual war for British started only with Churchill. Norway was a fucking joke and IIRC the reason why Chamberlain finally realized his mistakes and retired to promptly die.
Churchill disagreed with this assertion, along with some modern historians, basically saying after Munich Chamberlain was much more aggressive, and worked to do stuff like expanding the British army. As for Poland, the British could probably have done more, but its a lot easier to send troops to France than it is to a country on the other side of a hostile power. I highly doubt the British had the capacity to pull a D-Day style landing to assist the Poles in 1939, and they certainly had no way to help Czechoslovakia in 1938. You said yourself that the British invasion of Norway was a failure, and it is a lot closer to England than Poland was. More realistic was a French invasion of Germany while they were busy dealing with Poland, but they seemed pretty happy to let the Germans come to them. A quick look at the wikipedia page for Chamberlain suggests he thought that German rearmament would cause an economic crisis and so he put his resources into assuring that happened. Wikipedia also blames French delays for the declaration of war being made on September 3rd, which is only two days after the invasion of Poland began.
Yes... To make it worse, a multitude of people from as far back as the original Treaty of Versailles repeatedly warned both England and France (and basically every government who participated in the WW1 allied war effort) that Germany would rearm and return more powerful than before. France, consisting mostly of French people, ignored the warnings, and England was devastated economically and unable to really do anything. The same economic devastation affected most of Europe and effectively prevented nations from caring too much about properly sorting Germany out past the harsh surrender (which was pretty obviously a huge mistake, recognized by many people, both at the time and later.)
So you're arguing that letting Germany regrow was a mistake, yet trying to stop it from regrowing was a mistake? I think I get what you're trying to say, but
In short, the world created a monster and realized too late what it had done.
There's a distinct difference between this and Chamberlain wanting to see a Fascist Europe before war, which was my original point.
Also, IIRC, both UK and France and even US knew about Ribbentrop-Molotov (as in, the fact that Germany is going to attack, and possibly even more importantly, that the Soviets will too) pact as early as 24 or 25 August. They never told Poland. Allies so great at being allies, eh?
The British entered into a defensive pact with the Poles on the 25 of August. Otherwise I can't find any definitive evidence for or against your assertion.