I finally got around to looking at a Schistidium collected from the Taff riverbank in Cardiff, which I alluded to in a previous post on 4th December. It was growing on a poplar trunk in the flood zone (or just above it). Photos below.
Most of the leaves lack hair points but a few have them - these are toothed (see pic). I thought it might be apocarpum, due to the toothed hair points and long capsules, but the lack of hair points on most leaves concerns me. In this respect it more closely resembles platyphyllum, but the leaves seem too narrow for that (certainly narrower than my previous example of it which Sam identified).
Any comments welcome!