I currently have a 32A B curve RCBO in my house consumer unit.

6mm2 cable runs from this RCBO to the garage which is a run of less than 3m. Currently nothig is connected as a load to this 6mm2 cable.

I plan to connect the already buried 10mm2 SWA cable to this 6mm2 cable via a junction box. The SWA is 10mm2 due to the voltage drop across the garden.

I would like to then put in a shed CU at the other end of the SWA which is at the bottom of my garden.

This Shed CU would then have 3 x 6A RCBOs for a shed lighting circuit, a greenhouse lighting circuit, an external floodlighting circuit and a 20A RCBO for a double external socket.

We may want to add further circuits of up to 32A for a hot tub in the future.

The house has PME earthing (In old money) and there is a MET in the meter cupboard

One small fly is that the shed is a metal yardmaster so I plan to supplementary bond the shed metal work to the SWA's earth conductor (I propose to export the earth)

Now How do I sort out some form of discrimination between the house CU's 32A RCBO and all the RCBOs in the shed CU as I've never seen a time delayed 40A type C curve RCBO to replace the 32A RCBO with?