Slightly different take. It has been mentioned a few times that there is a more than reasonable chance that the RN or RAF could Sealion before it got out of harbour. This is sensible. Why take risks?
Could anyone on the UK side successfully put forward a plan to encourage an invasion? The first problem that I see is that the RAF can't risk losing air control because that will get your factories shot out and air control is a prerequisite for invasion.
As much of a cinch as it sounds, I can't imagine anyone actually advocating that Britain try to let Germany invade somehow so as to sucker them into defeat.
Both as a general principle and because in summer 1940 there's more than a bit of panic in the air. Germany has somehow cracked the secret of modern warfare (seemingly). Britain's first line of defence, France, was supposed to hold out forever, but here it's fallen in a matter of weeks. Are we really confident it won't happen to us next? The Germans are probably going to bomb us. Will the civilians hold up under that? And so on and so forth.
Of course, the more time you have to think about it, the more cold reality settles on you and the more you realize that the invasion just isn't bloody likely. In the real world, the Germans came to that conclusion just about the same time that the British did, more or less, so we'll never know what might have happened otherwise.
