I wouldn’t worry yet, the C is still an idea, no detail has been released and the previous industry consultation was abandoned due to Covid. I think clear guidance won’t be available until 2027 at the earliest. In my experience there will be numerous exemptions even (who knows) for Almshouses as a specific exemption from the Heat Metering Regulations was obtained.
Current exemptions only last 5 years anyway so registering anything prematurely would not be worth it.