What a nightmare this is turning out to be, but I'm making progress so I think I'm coming out of the woods now.
I'll put 2 pics up, before and then after at least 3 coats of paint under the deck.
The thing is people,
only the camera can pick these light bleeds up, you honestly cannot see any light bleed with the naked eye, not even in darkness with your nose almost against the deck - nothing.
But if/when I take pics of the finished ship in all her glory....................................

Left was last night, Right was this afternoon - Happy Daze.
Looked to try and find paint that omitted light and come across many model building forums discussing the exact same issue with LEDs showing through hulls, fuselage etc. - the most popular advice was a coat of silver paint.
I'm going to test the hull of course prior to top planking and after, and if it comes to it, maybe put a coat of silver prior to the black top coat.
If anyone out there in SOS land has any Do's or Don'ts it would be appreciated enormously.