Building Control
Completion Certificate, in your name, for the work undertaken. Confirm any conditions on it have been discharged.
Trade certificates
FENSA or equivalent for windows. Gas Safe for any gas work. Electrical certificate (EIC or minor works). HETAS for solid fuel. Ventilation certificate where applicable.
Manuals and warranties
Boiler, MVHR, kitchen appliances, structural warranty if applicable. Plus an operation and maintenance manual covering the whole work.