The majority of properties in the UK have an EPC ( Energy Performance Certificate), if a property does not have one or it has expired, customers will get one on survey.
You can use this service to find an existing:
Energy performance certificate (EPC)
Display energy certificate (DEC) for a public building
Air conditioning inspection certificate and report
The EPC will tell indicate what rating a property is.
7 bands in total, A, B, C, D, E, F, G
All properties that currently qualify are D, E, F G rated properties.
If a band can be improved by 2 SAP ratings, ie from an E to a D then it would qualify. In order to do this you will need to conduct the insulation measures first followed by the heating controls. It will then advise what measures can be installed along with the typical annual savings for the customer.