Having worked for the GPO and in numerous call center positions (including financial services), I would agree that normal practice when checking addresses is to use only the first line and the postcode. This is because the rest of the address does not have a standardized format that is universally used.
For example, my home address, if written in full, includes a house number and street name, estate/locality/district/village, postal town, county and post code. However, if asked to write out their full address, not everyone in my street would agree on everything bar the 1st line, post town and post code. Thanks to the original developer giving the estate its own name (presumably for marketing purposes), the local council and GPO trying to rationalize locality names, local snobbery (i.e. "we're not the same as the council houses") and GPO and local authority boundaries being different, there are at least four ways of writing the address in full, not forgetting that omitting the estate/locality/district/village and county lines is perfectly acceptable for the GPO to deliver mail.