I believe the appropriate word for the #45 and #145 Gateman Accessories is "iconic". There are relatively few items that achieve "iconic" status. The ZW, the Santa Fe F3, the Operating Milk Car, a bottle of smoke pellets, and the Operating Gateman all fit that category.
I understand the OP is in England, and may not have as much quick access to the knowledge base that we do, but caveat emptor.
Jon