I have come across your post while doing some research in to the mines in the local area. Pennygreen (llanidloes) consists of a old factory that has now been converted in to flats that runs along the river, There is also Penny Genygreen farm, and a number of Victorian house that still remain on penygreen road. As for the mines in the area there a 3 that are in walking distance of llanidloes, First there is Van lead mines, these mines north/east of llanidloes, Secondly there is byntail lead mines, they are located next to the dam just north of llanidloes. and then there are the mines that I am looking in to now. these are the closed to llandloes and as yet I have know name for. south of llanidloes. Hope this helps.
All the best
Trails Outdoor Pursuits