In most photographs P turret is facing the other way as is Q. This puzzled me until I realised most pictures are taken during peacetime. In war time or when expecting to engage the enemy I suspect the direction of the turrets were reversed as otherwise for P turret to engage on the starboard side it has to turn 270 degrees whereas if faced the other way it only has to turn 90 degrees.
So, yes, the gap is narrow and the crew could pass through the gap but in peacetime with the turrets facing the opposite direction there is plenty of space as the turret overhang at the rear is the opposite side. This give day to day advantages for crew movement but in action the crew wouldn't be running round on deck anyway.
Also for modelling purposes if I want to fire a four gun broadside I need to link the turrets in pairs, so A & Q facing forwards and P and Y facing aft so I only need to turn each of them 90 degrees each way.
In practice its a little complicated as I need to turn A & Q to port then Q and Y to port as there isn't clearance between the rear of the turrets and the adjacent guns. I suspect in real life they would elevate the guns to give clearance.
The ships were originally designed for 6 guns to fire forwards, 6 on the beam and 6 aft to give all round shooting. In practice neither P or Q could fire within 5 degrees of the centreline due to blast issues so forward aft was really limited to four guns.
There was limited room for P & Q to fire on each side but only if the adjacent turret was out of action. In practice (Falklands) they did give 4-8 gun broadsides but the blast effects were very unpleasant.
Typically ships of the period only fired 50% of their guns at any one time to reduce the firing cycle. A 12" gun can fire 2 rounds a minute but if each turret only fires one round at a time this drops to a salvo every 15 seconds, so a higher rate of fire overall.
Cheers
Geoff