Yes, to letterbox. But I think it should be clear that it's for Makerspace post, and that members need to have personal correspondence delivered to their own addresses.
Cigarette bin? Could this go in the garden area? Might encourage less smoking right by the door, which I believe has caused some friction in the past?
And...what about the dog 'waste' issue? Is it passive aggressive to put up a dog waste bin and bags somewhere in the entrance to the Bath Factory Estate? I've a feeling it's mostly the efforts of one dog, and I'm pretty sure I know the main dog-owning culprit is. Maybe a conversation and the gift of something like this easy/lazy amazon link would do it?