A semi-detached house has a prehistoric fuse box with rewirable ceramic fuses. It will shortly be replaced with a modern consumer unit. The existing circuits are:

1. Lights

2. Upstairs sockets

3. Downstairs sockets

4. Kitchen sockets

5. Cooker

6. Shower

The following circuits will be added to the consumer unit:

7. Central heating

8. Burglar alarm and CCTV

9. Outside lights

I have been informed that the best choice is a split load consumer unit with two RCDs and space for RCBOs. My intention is that circuit 8 has its own RCBO but what is the optimal way to allocate circuits to RCD A and RCD B? Also, should any other circuits have their own RCBO?