Blayneys of Cedewain listed in
the St Asaph Notitiae
In 1681 William Lloyd, Bishop of St Asaph conducted a survey or Notitia of each each parish in the diocese. The diocese consisted of eight deaneries, namely Bromfield and Yale, Cedewain, Cyfeiliog and Mawddwy, Edeyrnion and Penllyn, Marchia, Pool, Rhos and Tegeing. I was told about this by Kevin McKenzie 
A digital picture of the manuscript record for each parsish is available from the National Library of Wales website  [description and good starting point]. The rural Deanery of Cedewain  has the parish lists for Aberhafesp, Berriw, Bettws Cedewain, Llandysul, Llanllugan, Llanllwchaearn, Llanmerewig, Llanwyddelan, Manafon and Newtown.
Blayneys of Cedewain found in the 1680s St Asaph Notitiae surveys:
Number of souls
Ages under 18
Aberhafesp ?1681 Mr Edw: Blayney 7 4 1 ?1681 Maud Blayney 4 13 8 Berriw ?1681 Widow Blayney
5 8 3 ?1681 ?Anne Blayney [a] 3 ?1681 Richard Blayney 3 17 Bettws Cedewain ?1681 ?Rich Blayney [b] 8 16 14 12 10 8 4 ?1681 Moris Blayney 7 17 1686 Richard Blayney 5 1686 Moris Blayney 4 Tregynon 1681 Henry Blayney Esq 12 10 9 8 7 6 5 3 1681 Edward Blayney Esq 9 14 11 9 5 3 Here Henry is the son of Sir Arthur but I had Edward with no issue! No Blayneys were recorded in Llandysul, Llandysul, Llanllwchaearn, Llanmerewig,
Llanwyddelan, Manafon or Newtown 1n 1681 (or 1686)!
? Anne Blayney
? Richard Blayney
St Asaph early 1800s 
William Barker's "Families of Montgomeryshire"  lists the brothers Morris Blayney (sic) and Richard Blayney of Heigate, Bettws Cadewen (sic), with "Morris" having five chidren and Richard having six children alive in 1689. These are possible ancestors of mine - see Moris Blayney
Barker also gives enough information about Edward Blayney (of Hill, Aberhafesp), to identify him as Edward, son of Thomas, son of John, son of Sir Edward Blayney.
Household head Edward Blayney of Tregynon cannot be Edward, bp Tregynon, 5Apr1674, brother of Henry, sons of Arthur, son of Sir Edward Blayney, as this household head has 5 children, the oldest being 14 in 1681 (so born about 1667, 7 years after Edward).
Henry Blayney here certainly fits with Henry, son of Sir Arthur BLAYNEY, as this Henry died 10 years later in 1891 and had nine children, two possibly on or after 1681.
However, Henry's brother Edward had no children, so perhaps this is another Edward, EDWARD BLAYNEY - m by 1683 ELIZABETH ... (wife not named in 1672-81). 1902: ELIZABETH bp Tregynon, Wales 22 Jun 1672 (BT) 1903: JACOB buried Tregynon, Wales 25 Nov 1681 (BT) 1904: EDWARD buried Tregynon, Wales 16 Dec 1681 (BT) 1907: CATHERINE buried Tregynon, Wales 4 Jan 1682/3 (BT ?Skirmisher did have kids . Alternatively they could be Hen