[madjam002]

There are and they cost upwards of £20,000 a year for a license. There’s a reason why smaller delivery companies get the address wrong and that is probably part of the issue.

[_-____-_]

The official one provided by Royal Mail is called the Postcode Address File (PAF) [0].

[0] https://en.wikipedia.org/wiki/Postcode_Address_File

[madjam002]

That doesn’t provide any geolocation information (unless it’s changed recently?), for that you need OS AddressBase