On the bank holiday we went for a spin and ended up going over The Black Mountain, making a very brief pit stop at the old limeworkings of Clogau Mawr (SN722193). The tufa formations are quite remarkable at this site, as I'm sure the bryophytes are too based on what I saw in the five minutes we were there. Hymenostylium recurvirostrum (photo)was the highlight, the extremely dense cushions with Aneura growing over them. Although this area seems to be a well worked part of Carmarthenshire, it's a very easy place to access and see some really nice formations as well as good bryos.
There's some beautiful limestone scenery all along the road as you head east to Llygad Llwchr (eye of the Loughor, where the source of the river emerges from a cave), including great views of Carreg Cennen Castle.