If using non WRAS approved fittings was an offence I presume our regular
plumbing consultants would have backed up the original poster.

For your info: Following is extract from the Regulations: (With respect
I am coming to the conclusion that your regular plumbing contributors
wouldnt know the regulations if they fell on them)

1 Plumbing systems to comply

Plumbing systems must be designed, installed and maintained to meet the
regulations' requirements. Plumbing materials and fittings must be of
a suitable standard. It is not illegal to sell unsuitable fittings and
appliances but to install one would be illegal, so check suitability
before purchase. The regulations list the standards which fittings must
meet and the Water Fittings and Materials Directory, published by the
Water Regulations Advisory Scheme (WRAS)

Reading the web page, it looks more like a consultancy firm.

If you would care to read it again you will see it is a Govmnt funded
scheme to protect the health of the public when it comes to the
conveyance of water.