I think a sea lion would have less than 10 % chance of success against a cautious UK.
The first turn you sink everything in the North Sea and move your fleet to sz 112 (in 111 the UK can will be able to block an invasion as you won’t be able to kill all his ships. With luck you should be able to kill everything that’s can be a problem for you in turn 2 w/o loosing any planes. You also need to kill the fleet of Canada so they can’t bring extra units to England. You land all your planes within reach of the UK. You mop up France and other places with land units. Build is 1 CV (needed to defend your fleet in range of the RAF and the Gibraltar fleet (with is very unlikely one will be able to take out) and 1 TRS (could build a bmb instead but I think the extra hit is usefull and there are already to many planes that can be shoot down by the AA).
The UK places one ship to block ur shore bombard and build 7 inf and 2 art (or 3 inf and 5 art if he is brave). Also lands his TAC in the UK.
Ur turn 3, you attack with 2 tanks, 2 inf and 8 planes. He defends with 9 inf, 2 art, 3 figs 1 tac an 1 aa. The chanse of success is less than 10 %.
Might be better to fake and attack and then not doing it, just building an CV more or less forces the UK to build inf the first turn and allows the german to keep destroying some fleet.