This file is a best fit lookup between output areas (December 2011), electoral wards/divisions and local authority districts in England and Wales as at 31 December 2016. (File Size - 10 MB)REST URL of Feature Access Service – https://services1.arcgis.com/ESMARspQHYMw9BZ9/arcgis/rest/services/OA11_WD16_LAD16_EW_LU_c6478a7e75c347e6a4f8743fa86b50de/FeatureServer
For more information and an overview of best-fitting follow this link - https://geoportal.statistics.gov.uk/datasets/f0aac7ccbfd04cda9eb03e353c613faa/about