Good to hear from you Dan. Thanks for your tactful query about this unlikely bit of mapping. :)
“Unexpected” That’s exactly what we  thought when we were standing in front of it. Hard to believe they would put one down there. But the format and info in the window all looked right - reference number, collection times etc - and the metal day insert was set to the right day. I wish I’d taken a photograph to send you. But if there is another box somewhere with the same number then it must be a private delivery box I suppose. Despite its unlikely position it all looked so right that we decided we had to map it. But I don’t mind if you delete it. Im not an expert on post boxes. Cheers. John. 