Hi Bradley,
I realise it's been more than a year since you requested information on Powyson, -but I came across the following references recently during my own research,
- hope these are of some use to you:
(from the Gwynedd Archives Service (Caernarfon) on-line catalogue: "Rhagorol"):
XD9/830 1908 Awst MEMO: NODYN oddi wrth Mrs. Jones, Powyson, (aelod ym Moriah). Hefyd, nodiadau ynhgylch ei gwr, Thomas Jones, a fu yn flaenor ym Moriah.
(Translates as: XD9/830 [= Gwynedd archives document no.] 1908 August Memo: NOTE from Mrs Jones, Powyson (member at Moriah [Chapel]). Also notes regarding her husband, Thomas Jones, who was a deacon at Moriah).
Book (in Welsh): "Gwyr Enwog Gynt (Ail gyfres)", E.Morgan Humphreys, Gwasg Aberystwyth (1953) :
"Powyson" (Thomas Jones) is mentioned in anecdotes three times (pp.111, 112, 113) in a chapter on "Eifionydd" (John Thomas):
p.112 (translated): ".....and it was in Machynlleth that he [Eifionydd] came into contact for the first time with another young publisher, Thomas Jones, "Powyson", who became a life-long friend........"
In his chapter on Beriah Gwynfe Evans (p.124) E Morgan Humphreys states that "Powyson" started at "Y Genedl Gymreig" about 1879.
According to "Carneddog a'i deulu" by E Namora Williams, "Powyson" (Thomas Jones) was the editor (and co-owner?) of the Caernarfon-based Welsh language newspaper "Y Genedl Gymreig" (p.60/61), and was still in charge in 1910/1911.
Postcard (in my possession), postmarked 31/12/1906 from "Alafon" to "Mr & Mrs Powyson" (Mr & Mrs Jones), Bryn Powys, Victoria Road, Carnarvon (as spelled on the postcard!) wishing them a very happy new year (in Welsh).
A Google search led me to
http://www.amazon.co.uk/exec/obidos/ASIN/B0000D2B0P/onthewebcom-21/202-3209268-0985428, listing (sheet?) music by John Henry Roberts and words by "Powyson" (Thomas Jones).
Hope this helps - let me know how you get on.