It is recommended not to have 3 or more wires coming out of a MCB or RCBO.

The simple reason is because one of the wires can work loose as it's not to get the screw terminal to grip all three wires with equal force.

I would put that single radial run on its own MCB.

In fact, I would use a RCBO for 3 very good reasons but you would have to wire the RCBO upstream of the RCD. (The main one being the boiler still continues to work stopping the house from freezing if the main RCD trips so you don't come back to a flooded house. The second reason is if the washer develops a water leak, it does not take out the RCD and affect half the house.