This has been discussed in great detail between historians. Luckily, I've been privileged to be a part of these discussions, I've learned a ton of information that simply can not be expressed when reading books and other original sources.
It has already been mentioned that *if* the Germans had bested the RAF, the remaining RAF aircraft would have been put far beyond the reach of the Lw while waiting for their chance to go on the offensive vs German supply lines, etc. The RN would have been able, probably, to fend off any German attempt to land or at minimum "slam the door shut" as someone said earlier.
The Germans would have lost either way, they didn't have the Navy nor the range in the air to fully commit to conquering the UK.