Jim. I think you take a partisan view of the civil war. It could be argued it was a proxy war for the Soviets and Nazis but only in a half heated sort of way. Despite communist recruitment of the volunteers, reports suggest training and equipment was deficient, despite a kind of Soviet participation. This seems to have been more to do with leaders and commissars but limited commissariat.
Britain was slowly beginning to realise that Hitler was an increasing threat, but initial threats were thought to be in the East.The Defence Requirements Sub-Committee costed the requirements at 75million. Chamberlein cut it to 50. A second report was issued in 1935 insisting on acceleration and more aircraft. A third report was issued in 1936.
It was DECISIVE. It looked at war with Germany, Japan and Italy; the report contained a stark warning: Britain could not win this coming war. Therefore, it suggested, appeasement was a good idea. To be in the situation outlined it was no surprise that Britain was terrified that the Spanish Civil War might escalate beyond it's borders and that
rearmament at that time had hardly started, and that when it did start the initial aim was purely deterrence, not battle. I would posit the big picture had many more constraints on British courses of action than you allow for. In essence we were weak and unprepared for a total war. By Aug 1939 the Molotov ribbentrop pact destroyed the hope of a pact with Stalin, who hoped that Germany would fight on a western front and enable the soviets to become stronger. This made the British and allies position even more precarious. The situation throughout the 30's was complex and constantly changing and cannot be easily summarised in a couple of paragraphs. You may have detailed knowledge of the civil war but many other external factors dictated the actions of other governments that directly impacted the civil war.



https://jamespetersnell.wordpress.com/2015/12/20/404/