I used MEM (now Eaton) Memshield2...

http://www.cucumber.demon.co.uk/cu1.jpg
http://www.cucumber.demon.co.uk/cu2.jpg

Bags of space inside. Very nice consumer units to work with.
Probably not cheap compared with domestic consumer units.

I liked the way that example had a box before the CU which reduced the
number of wires in the CU. Wd that be OK in a domestic installation so
long as there is (as in your example) no gap between the 2 boxes (and of
course the singles are rated to cope)?
--
Robin