Take away British support and the Poles are going to be a whole lot more accommodating about Danzig and the Corridor. Originally German demands were for Danzig to be restored to the Reich, for a new highway and railroad to be built through the Corridor with extraterritorial rights, and for Poland to join the Anti-Comintern Pact.
Knowing they had a British guarantee Beck and his fellow colonels felt secure enough to take a hard line stance and flat out reject all demands. Take that away and they probably give in to them instead.
Up until the Poles began playing hard ball Hitler likely saw them as useful puppets. He would have made more demands but allowed them to keep their nominal independence so long as they did as they were told. If the British, and under them the French, decide to be accomodating then Hitler will likely go to war with the USSR with Poland, Italy, Hungary, and perhaps Rumania at his side. The rest of the world would stand aside and let them fight. The war would likely begin in 1941 or '42.
With no pact between them Stalin will not be lulled and not be surprised. The German Army is also going to be much weaker without the resources of Norway, Belgium, France, and he rest of Western Europe to draw upon. They will also have much less combat experience.
Likely it is a long bloody war where the Germans and their allies don't achieve near as much as in OTL. The Soviets would triumph but won't be allowed to overrun Germany and Europe, the British would likely moderate a peace where they swallow up the Baltic states and some of Poland, East Prussia, and possibly Rumania.