if not properly backed up by italian and japanese skilled players Germany will be trampled and steamrolled about 2 weeks after her initial attack against poland. To achieve victory on poland the reich will have to send in around 60/80 divisions while she will only be able to keep 20/30 divisions on the west front France and England would have amassed 100/130 divisions in France and would simply steam roll the left overs of german strength on the west side of the reich. What saved the Reich from an utmost defeat in 1939 was that none of the nearly 60 French division forming the maginot line and back up troops moved.... There was nothing in front of them to stop them but no French or English minister would have sent their troops first in fight for Danzig.
I really don't think the British would be able to afford to send 100/130 divisions to France. Even if they did attacking the German defenses would be suicide. I am pretty sure the Germans can improve the defenses on the border of France to make sure just in case the British do do that then they will be cut down. If the Germans do bring their entire army to bear on the allies and they take France, Britain could be in a dangerous spot if they lose anywhere near all or half of those divisions.