Wiring regs question

You have exactly the same situation as any place with two way switching of the hall and/or the landing light. So it's a common situation to have two separate circuits at one switch position. So perfectly acceptable from a regs point of view.

I have 4 lighting circuits here:

loft

I have a double gang back box in the hall way with 5 switches on it. one is for hall light, one is for landing light and these two switches are on 2 different RCBOs. These two two watch switches are in the left half of the double gang back box.

The right hand half of the back box has 3 switches for 3 outside lights which is on a 3rd RCBO.

I have a mental partition in the middle of the double gang back box to at least mechanically separate the outside lighting wiring from the two indoor lighting circuits.

I'm reassured. I've just realised I had the same situation in a previous three floor house, where the middle landing had two way switches for both the stairs going up and the stairs going down. It just seemed counter to a "common sense" view that it's best to have a single isolator for any wiring enclosure.

if they are both on the same phase?

That's fine. I would put a label inside the switch box warning that 2 circuits are present.

Owain

I have seen three phases in one lighting switch box. It was a mechanical workshop with fluorescent lighting and rotating machines. There was a permanent warning label on the outside. John

If you have not "borrowed a neutral" this perfectly normal.