Fuse board installations are a big part of my work load.One of the main reasons to fit a twin RCD fuse board is to comply  with 17th edition regulations which states any circuit which is buried less than 50mm in a wall in a domestic property will need 30 Ma RCD protection .Although before that it was required for shower and power sockets outside .I only use Hager fuse boards after the job is completed issue the Napit installation certificate which comes in a PDF form which can be emailed and saved to computer,I  also keep copies which are also backed up if they are required in the future. Now 17th edition Amendment 3 has come into force  all new fuse boards have metal enclosures and lids giving fire protection