Laurie, the chances of finding plot numbers for Llanwonno are slim to say the least. The Church and the pub - The Brynffynon Hotel - are the only two buildings there. Others have said, as I have, the Graveyard is totally overgrown and has been for more years than 20 which was the last time I went there. My last memory of who may be responsible for the church is the Church in Mountain Ash, but this could have easily changed. I have several members of the Davies & Evans families buried there and it is worth noting that Llanwonno is about 5/6 miles from Ferndale and roughly the same to either Ynysybwl and Mountain Ash. Good luck.
Brian - Blaenllechau born and bred.