Consumer unit in a flat

Hi the answer is no for example you could have a consumer unit filled with rcbo's rather than a dual rcd hope this helps

Technically your consumer unit doesn’t need to be split load dual RCD, as long as any circuits where the wiring is buried in the wall less than 50mm and not mechanically protected are RCD protected. Good practice for flats dependant on size and number of circuits would be to install a separate RCBO for each circuit, as most flats generally have only 4/5 circuits. This means that if a fault occurs on one circuit, this is the only one that will trip leaving the others on. If you did install a single RCD covering all circuits, of a fault occurred you would lose all circuits until the fault was rectified.

Hi there You only have to upgrade a consumer unit to the current wiring regulations (which also requires it to made of metal) if you are changing the design of the electrical installation. This would mean adding a new circuit to the installation from the consumer unit, or changing something within the unit, or perhaps moving it. Even if you needed a new circuit installing, the electrician could install a new small one-way metal clad consumer unit next to the existing one. It should only be marked as a "Code 3" on a periodic inspection (this means requires improvement) if the consumer unit is under a wooden staircase or in the path of the only escape route from the building.

Only if it is being changed.

The dual RCD option is mostly for practical reason but now a days considered good practice as well. The regulations though don't say anything agaist using a single RCD. Now, if you do any works on a circuit, that circuit needs to be brought up to date with current regulations and only that circuit. If your current consumer unit is newest type with brakers (doesn't matter how old) that can be solved with replace the circuits MCB with an RCBO if it's not RCD protected. If your consumer unit is of the older type with the fuses then it may need to replace the whole unit. The latest regulations also require that all sockets in a house must be RCD protected regardless of how the cables have been installed. For older installations though there are no requirements from the regulations to be brought up to date as long as no electrical work takes place. Long story short, if when the instalation was first made was up to date with the then regulation you are not required to bring it up to current regulation. For rental properties though it's always a good idea.