exactly what IS "posh"? Rich? Fancy? Snobbish? Elegant? All 4? None of the above?
Posh is up market
as in 'expensive'?

"Yes" is the easiest answer to your second question and "All 4" to your first, Bill.

The apocryphal Port Out Starboard Home which is the best place to be on a fat cat fancy ocean liner! apparently derives from the ships of the East India Company between Britain and India but I suspect it to be in error.

From England to Rio, starboard cabins get the pm sun.
From Rio to India, port cabins get most of the sun, whether am or pm.
And vice versa on the return run.

But I'm certain the British 'catters will dig a lot deeper than I could in such matters.

Cheers, Rowan