That is fine for double pole isolation as is the use of a dual rcd consumer unit.
Clearly you are offering advice outside of your depth of knowledge and/or experience.. :shakehead
I believe on multiple occasions in the past you have commented something along the lines of...
"You never do, or rarely do, or don't do much" Domestic work?
So you may not fully grasp the compliance requirements of regulation 314.1 (i)..
specifically the comment... "MINIMIZE INCONVENIENCE IN THE EVENT OF A FAULT"
its on page 50 if you need to double check... :C
A faulty fluorescent fitting, (Neutral->Earth short), in a garage killing the power to the socket that also supplies the internet router is VERY inconvenient.....
especially when its off and you can't reset it and the electrician can't get there till tomorrow..
As is a failing freezer compressor in the kitchen knocking off the upstairs lighting and the combi-boiler...
Or the pond pump and water feature lights failing while you are away for a summer weekend visiting family..
So you come back on Sunday night to no lights or power to the fridge that has got warm!!
Plus in each of the above, the possible half a day to a full days labour paid to track down the cause of the fault can be expensive and inconvenient compared to the time & initial installation costs of a full RCBO CU..
You may well have a different opinion of the concept of "inconvenience"..
but in my experience, (trading self employed since Feb 1999), Dual RCD board are a minefield of inconvenience!!
And anyone still installing dual RCD boards is most likely lacking an understanding of the realistic problems they can and do cause..
Had a call yesterday from a customer I initially visited in 2015...
having problems with power tripping off.. (existing CU.. NOT installed by me.. but NOT full RCBO!)
Including loosing sockets in kitchen...
If it wasn't inconvenient they would NOT be calling me!
I am going back Friday afternoon to see what I can find...
depending upon how long I am there..
It may well have been more cost effective to have gone full RCBO initially!!
The concept of a design where a faulty circuit can remove power from a perfectly good circuit beggars belief...
about as sensible as designing a car where any single failure will illuminate ALL warning lights on the dashboard!
:C
Guinness