Have you tried the record office in Carmarthen. They may well hold records for the chapel in Drefach, Llanelli. At the moment I cannot remember the name of the chapel. The chapel is not located in Drefach it is in a neighbouring village. There are Tinnuche family in Llangennech as well. The records you need then is for St Gwynog's Church, Llangennech. Again available at the Carmarthen record office.