Always looking for the odd places you might find things, but 99% of the time with no luck, I came across an ad in a free issue local with 'Post office artefacts' for sale.  It was a week old but gave it a go.   The chap said he had a 'tin sign' that was red and had telephone written on it, and that he still had it, and others, but they were at his fathers.   I went to his address and he showed me the red post office telephone sign and some post office ephemara which I duly purchased.  He told me that his father had worked for BT, and picked up things.  He had already sold a few things off already, signs with brackets on them he said. Asking if it was ok to have a look at anything else we went to his fathers house and to his shed., inside were the signs shown. Apparently the other two signs he'd sold had pointing fingers with an image of a phone on them, which was a shame, but quite happy to get what I got. Still  well worth still scanning the locals!!