[They were bled dry in 2 world wars and fought alone]
Actually WW1 was a French - German affair. The Brits saw the eventuality of that was and planned a modern 5 division-strong (British) Expeditionary Force that, had it not been there, would have spelled the defeat of France in 1914. Even so, the Brits dithered for several days before declaring war.
In WW2 the only choice Britain had was to fight or cut-a-deal with Germany. Had they ‘cut-a-deal’ I’m pretty sure the Soviets would have been defeated and then Britain has major problems (kinda like now with Germany having it’s hand on the Brexit meat-grinder).