Wiring up new light fitting
Sussed It

From trial and error located live switch. It was one of the 3 all red cables.

This wire went into live wire junction from fitting

Next was 3 earths into earth for light fitting

Next was the 2 black neutrals into neutral from fitting.

Finally left with 2 red cables and they went into the 4th hole on the junction box on there own.

Power on... Light fitting working with correct brightness and upstairs and downstairs switch both working to turn light on and off.

Only took me 3 days on and off.