Note that this is not an official postal address.
There are no official postal addresses for numbers 38 or 40 (although entrances do exist at these locations and may be in service for what are Flat 3 at 39 and 41 respectively). The only official postal addresses are for flats at numbers 39 or 41. Post for numbers 38 or 40 is usually bundled with and delivered with post for numbers 39 and 41 respectively.