QUOTED: The family came from Llanidloes, Montgomeryshire. The electoral register in Glamorgan for 1919-1935 shows a Thomas Edwards and Annie Edwards residing there. Coincidentally this was her mothers maiden name as she was Sarah Edwards born in Ysbytty in 1864.
My first thought was this William you found on the electoral roll could be a brother of Sarah? So I looked on the 1881 census and found this: Keep it on file as this information may help you a little later on
1881 census:
Dwelling: Highgate Street
Census Place: Llanidloes, Montgomery, Wales
Source: FHL Film 1342317 PRO Ref RG11 Piece 5480 Folio 36 Page 11
Marr Age Sex Birthplace
Hugh EDWARDS M 50 M Llanidloes, Montgomery, Wales
Rel: Head
Occ: Lead Liner
Sarah EDWARDS M 47 F Llanidloes, Montgomery, Wales
Rel: Wife
John EDWARDS 15 M Llanidloes, Montgomery, Wales
Rel: Son
Occ: Wool Sorter Apprentice
Thomas EDWARDS 12 M Llanidloes, Montgomery, Wales
Rel: Son
Occ: Scholar
Sarah J. EDWARDS 7 F Llanidloes, Montgomery, Wales
Rel: Daur
Occ: Scholar
But I know that this Sarah was probably too young to then marry in 1884!
In the Wales region in 1881, there were only 3 Frederick Norris's listed:
NORRIS, Fredk. Wm. Son <1862> Birth: Devo Torquay
Census: Glam Llandaff
NORRIS, Frederick Son <1865> Birth: Wilt Chippenham
Census: Monm Bedwellty
NORRIS, Frederick Son <1879> Birth: Cardiff
Census: Glam Llandaff
I think you will have problems narrowing down your search for him in the timeframe you are after simply due to his occupation. This would have been a common occupation and a town / Village will be needed to try to find out anything about him.
Have you thought about Trade directories? even then though a Town or Village will be needed.