Britain was never the goal. We could have stayed out of both wars.
Also I think if you wiki 'war games' or something to that effects, German and British generals got together after the war and acted out what would have happened upon the German invasion and they would have got just north of London and been stopped.
and i'll point out that the Sandhurst games were rigged in favour of the Germans, in that the RN was'nt allowed into action until after the germans had landed