Provide a series of Local Studies Notes with Sources for Family History and a Guide to Holdings
Libraries and Museums in Powys list on the Powys Archives site
Hereford Archive Services holds Hereford diocesan and parish records (bishops' transcripts, probate and tithe records and parish registers) for various parishes on the Radnorshire/Herefordshire border.
The National Library of Wales. Aberystwyth. The major repository of information relevant to Welsh genealogy, such as Bishop's Transcripts of Parish Registers, Marriage Bonds and Allegations, Nonconformist Records, Probate Records, Tithe Maps and Apportionment Schedules, Legal and Administrative Records, Estate Records and Personal Papers, Pedigree Books, Newspapers, etc.
Llandrindod Wells Library
Cefnllys Lane, Llandrindod Wells, Powys, LD1 5LD
Telephone: +44 (0) 1597 826870. The library hold copies of most Radnorshire Census Returns 1841 to 1901.
Powys Museum Service
The National Archives has details of many archive repositories in the UK with links to their web sites, if any.
The Royal Commission on the Ancient & Historical Monuments of Wales (RCAHMW)
Apart from their online Archive Catalogue there is the Chapels database which will eventually list all known nonconformist chapels in Wales.