Also, just to make it clear, EVERYONE before the war had this holy grail idea of the bomber that's too fast to be intercepted. You have to understand though that, just like the holy grail, it's a fundamentally impossible to achieve idea. Because, if you think about it, if you manage to actually make an airframe that's faster with two (or four) engines than an existing interceptor, you can take the same airframe, eliminate the extra bomb load and crew, and put cannons in its nose, and call it a fighter. Now you have a fighter that's just as fast.
And all countries in the world had done just that: make a twin engine fighter if the technology ain't there yet for a single engine to keep up with a given role.
E.g., while we talk about Hurricanes and Spits and so on, what the RAF ALSO had since 1937 was the Bristol Blenheim which had demonstrated a top speed of 307mph. It wasn't very agile as a fighter against escorted bombers by '40, but it could mess up an unescorted bomber real good. And as was proven later, it could use higher caliber auto-cannons in the nose, with none of the problems that initial experiments with putting them in the wings of lighter planes had.
I could give other examples, but basically everyone seems so enchanted by the really good fighters, that they forget that the UK had about two dozen different fighter models during and right before the war. Were they as good as Spit or a Hurricane? Well, no. But if you needed something to shoot bombers out of the sky in '38, you could jolly well ramp up production of those until someone designs a Spit.