They are publishing the new standards as an amendment to the Domestic Building Services Compliance Guide, which can be found at https://www.gov.uk/government/publications/conservation-of-fuel-and-power-approved-document-l. From April 2018 the new standards will apply whenever a boiler is installed in an existing heating system anywhere in England. This means when households in England replace an existing boiler, or purchase a boiler for the first time in an existing dwelling, they will start to make savings right away.