CU needed for outbuilding

[Observer]

I have built a small garden toilet ~2m away from the house. The builder has laid flexible ducting from an external power socket, that is fed from from an RCD protected CB on the main CU via a RFC, to teh inside of the building. I will want to run a light or two (LEDs) and a small 2kW water heater.

I have two questions:

1. Is cable run in 2.5mm T&E adequate (the ducting is below patio slabs so zero risk of damage)?
2. Does the outbuilding need its own CU with two final circuits or can an FCU fused down to 5A be used for supply on to lights in 1/1.5mm T&E or flex? I am planning to run the heater on a boost timer which is itelf an FCU.

 

[Taylortwocities]

Oh dear.

You can’t run T&E like that. SWA is your option.
Your socket will already be a spur, so you’ll need a new 13A FCU at the point where the spur connects to the ring final.

FCU with 3 or 5A fuse for the WC lights.
Why on earth would you have a separate CU for one light and a heater????

 

[Observer]

Oh dear.

You can’t run T&E like that. SWA is your option.
Your socket will already be a spur, so you’ll need a new 13A FCU at the point where the spur connects to the ring final.

FCU with 3 or 5A fuse for the WC lights.
Why on earth would you have a separate CU for one light and a heater????

Thanks for clarification. I thought SWA would probably be needed but thought I would ask someone familar with regs. I can't see why a CU would be required but again, thought I should check.