Imagine France falls, Germany manages to keep the whole of HSF and knocks out Battle Cruiser squadrom and 5th Battle sqadron at Jutland and they managed to acquire much of the French fleet could Germany have invaded Britain circa 1917?
It's even more impossible then in WW2.
Tough, on a lot of levels.
I mean, first you have to get there. (no small task but doable, assuming great German luck). Ok, let's say the Kaiser wins the lottery and manages to get his troops ashore.
Now what? This is WW1, so roll out the trenches, quick firing artillery, machine guns, and gas. Not the stuff you want for a quick moving invasion of a small dense island. Not to mention, where are you going to pull the troops from? France will like this, and I can't see the UK rolling over.