Great photo - I think I can make out 6 species in that frame.
I think there are 7 - fancy a go at it?
Pellia epiphylla, Oligotrichum hercynicum, Diplophyllum albicans (the easy 3, I hope), Solenostoma gracillimum (assuming that slender shoot at 4 o'clock is that and indicates the bigger one at 6 o'clock isn't Nardia), Pseudotaxiphyllum elegans (5 o'clock), Ditrichum heteromallum or Dicranella heteromalla, perhaps a bit of Calypogeia fissa at 6 o'clock. You have the advantage of having actually been there, Barry!
I got most of those but have to confess I thought the Pseudotaxiphyllum was a Hypnum.
It might well be - it's very falcate :-)
The seven I know are definite are Pel.epi., Oli.her., Dip.alb., Dic.het, Hyp.jut., Cal.fis. & Sol.gra. I never recorded Dit.het. or Pse.ele. at this spot and I suspect what looks like the latter is just young Hyp.jut.. I don't do non-fertile Dit.het., so if you can see it there for definite I'd be pleased to find out how to spot it vegetatively. Id's from photos are not always that easy so that's pretty good going.
I note that almost all Glam records of Olig.herc. are post 2000 - in fact there is only a single pre-2000 record. Given its distinctiveness, records suggest this is a species that may have increased in recent decades.
Much of the narrow-leaved stuff resembles Ditrichum heteromallum, though it's hard to say quite why - something about its gloss and straight leaves on many shoots. In the uplands it's worth seeking sporophytes to confirm Dicranella heteromalla as well as Ditrichum heteromallum, as the latter is widespread (at least in Carms) in the habitats favoured by Oligotrichum.I'm not sure that Oligotrichum has increased recently, but it might have since the 1960s/70s when Tony Smith and Roy Perry did much of the past Glamorgan recording. It is favoured by disturbance so thrives by forestry tracks. Bear in mind that forestry was undervalued as a bryophyte habitat until very recently so its regulars were often under-recorded.
There was some fruiting Dicranella het. on the opposite bank, but it's perfectly feasible the foliage in the photograph is as you suggest Ditrichum het. I'll continue to only record these two where capsules are present, but I'll bear in mind the association with Oligotrichum and search more closely for capsules.