Download data from different websites for comparison

I need to access the API for this website https://www.gov.uk/find-energy-certificate. I then need information for 3 towns, Burnley, Accrington, Blackburn to see which entries exist on the register. I then need you to access any other website that has a list of all the properties that actually exist in these 3 towns. Perhaps postcode finder or census site or something similar. But some way of capturing all the properties that exist in these 3 towns. ( full address)These will then need cross referencing against EPC register. What i am trying to determine is, which properties actually exist but are not yet on the EPC register ( as per that link) Any questions let me know