I had sketched out an idea of Churchill rejecting appeasement and instead making Anschluss the last acceptable German gain in Europe and so giving guarantees to the Czechs and not the Poles. This would led to going to war over the Sudetenland Crisis while Germany still hadn't re-armed properly (relatively small army, few -109s or PzIIIs in service). The respectable Czech Army holds the Sudeten fortifications while the Allies hit the thin German lines (4 regular divisions, 13 freshly mobilised reserve divisions according to OTL German plan) in the still un-finished Westwall.Stop believing in myths.
Chamberlain was the driving force behind the 1937 rearmament, and if you make the mistake of putting Churchill in charge, then you'll get Paul Boulton Defiant aircraft and more battleships.
But then I realised that was utter rubbish - the French were never going to attack, not while Gamelin is still in charge. If the Churchill coming to power POD / Butterflies somehow result in Prételat (or similar approved French General) becoming French C-in-C then maybe it would work, but if not it is probably going to all go wrong.