To add ot that, the "simple" numbering scheme is usually denoted by e.g. "9/8" - Building 9, Flat 8, (which depending on the building layout might be 9 3f2 or 9 2f4). Infuriatingly, many postcode systems will autofill the "9/8" format into an immutable address field, and then reject the address with a forward slash in it...