As David says, the long-running county historical journal,
Montgomeryshire Collections, probably provides the best store of online information about Aberhafesp in the years pre-1800. William Valentine Lloyd's series of articles about the families of the county's successive high sheriffs is a particularly useful source.
The old family who lived there went by the surname Morgan, but they died out in the male line early in the 18th c. Lloyd has some info in
Mont. Coll. vol.9, starting at p.99 (including some anecdotes and the text of MIs in the church). In 1876 the articles up to the sheriff who served in 1639 were re-published as a freestanding book, and Anc***ry.com's databases include a scanned copy -- so, for those with access, that is an alternative way in. (To use that route, enter
Montgomeryshire and
sheriffs as keywords into the "Card Catalogue" search screen, then on the next page insert Morgan as the surname, and select the resulting hit for p.517.) As mentioned there, the heiress was Abigail Morgan, who married Walter Waring of Owlbury near Bishop's Castle; but it seems the couple had no surviving children.
After suspending his series of articles in Mont. Coll. at vol.9 (the ones separately published), W V Lloyd took up his pen again and produced a further batch, starting in vol.27 (1893) -- and a piece on pp.169-171 of that volume reveals what happened on Abigail Waring's death.
As Gnu posted in Reply 4, citing Aberhafesp BTs, she was buried there on 27 Dec. 1753. Lloyd's
vol.27 article states that the joint residuary legatees of both real and personal estate named in her PCC will were:
her cousins, Henry Shere of Lombard Street, London, goldsmith, and Elizabeth Proctor, wife of Mr. Robert Proctor of Botolph Lane, London, merchant.
In fact, the preceding volume of Mont. Coll. prints Abigail's will in full
here -- and, as a bonus, a browse through the surrounding pages will take the reader to several of the family's earlier wills proved in the PCC. So no real need to let TNA have their will fees.
In summary, it does seem that the later Proctors of Aberhafesp Hall probably had a blood connection with the Morgans -- assuming that they did indeed descend from that marriage between Robert Proctor and Elizabeth. (I see that the Anc***ry.com database of LMA London marriages shows that a Robert Proctor of St Botolph Billingsgate and an Elizabeth Ellis "of the same parish" married by licence at the Bridewell Chapel, on 24 July 1740 -- Ellis being at least a Welsh surname, albeit not Morgan; so a possibility for a female-line cousin of Abigail's.
*)
None of which, I fear, has revealed what has become of the main Aberhafesp Hall estate archives. Absent a response on this forum, it might be worth trying to tap local knowledge via an enquiry in the Powys FHS or Montgomeryshire Genealogical Society journals. Beyond that, as A2A has failed to locate much, I am afraid one would have to undertake the time-consuming but often rewarding task of approaching the successors to the firms of solicitors involved, to discover what might still be in their dusty basements.
Rol
* ADDED FOOTNOTE : I have seen some further circumstantial evidence that improves the odds of this being the right marriage. Towards the end of her will Abigail Waring made a number of smaller pecuniary bequests, and among them there is this paired legacy: "unto my cousin Jonathan Ellis of Botolph Lane, London, Esquire, and unto William Proctor, Esq., the sum of £20 apiece to buy them mourning". And among the (very sparse) baptisms at St George's Botolph Lane are those of William Fownds Ellis (30 Jan. 1705/6), Elizabeth Ellis (22 Mar. 1707/8), Jane Ellis (19 May 1709), Francis Ellis (28 July 1710) and Ann Ellis (24 Nov. 1715) -- all children of Jonathan Ellis and Jane his wife. The household seems to have often been living out of town on the south bank of the Thames, because on 18 Sept. 1709 "Jane daught'r of M'r Jonathan Ellis of S't Botolphs Billingsg't. London" was buried at St Alfege's Greenwich; on 22 Feb. 1715/6 Anne may well have been the "Anne d. Jonathan Ellis" who was buried at St Olave's Bermondsey; and then on the following 13 July "Wm Fownes s of Jonathan Ellis March:t from London" was buried at St Nicholas's Deptford. Finally, the father too was buried at St Nicholas's Deptford: "1758 … August … 8 Jonathan Ellis merchant from Botolph lane London". (Unfortunately I have not identified a plausible marriage entry to provide evidence of the maiden name of Jonathan Ellis's wife Jane.)