1.  Eleanor BEAUCHAMP was not the second wife of Sir John BLOUNT and she was not mother of Walter BLOUNT.  Walter's mother was Isolda MOUNTJOY, Sir John's one and only wife, as per email from Kyle VanLandingham:

Last year I obtained the pages from Complete Peerage, Vol IX, which show the Blount line from William le Blund [le Blount] who d. 1280.  The line shows that William's grandson, John le Blount, m. Isoude [Isolda] Mountjoy.  Walter le Blount who m. Sancha de Ayala is clearly shown as the 3rd son of John and Isoude.

2.  LDS.  Family Search: Internet Genealogy Service:  AF - Ancestral File (online at FamilySearch.org).  The LDS does not accept patron submissions prior to 1500.  All pedigrees in the Ancestral File prior to 1500 were done by the LDS Medieval Studies Unit in Salt Lake City, UT.

3.  Helen M. Blount Prescott.  1902.  Blount and Blunt.  Press of W.F. Roberts, Washington, DC.  [This is not a book, but a one-page pedigree chart.]): 

Sir Walter Blount, slain 1402 (sic) at Shrewsbury while wearing the Coat Armor of his King.  See Shakespere's Henry IV. Sancha de Ayala, of an ancient family of Spanish Grandees descended from don Vela de Arragon, 1074.

4.  Gary Boyd Roberts.  1995.  Ancestors of American Presidents.  New England Historic Genealogical Society, Boston, MA.

5.  Sir Bernard Burke.  1883.  A Genealogical History of the Dormant, Abeyant, Forfeited, and Extinct Peerages of the British Empire. New ed.  Harrison, London.  See excerpt posted at the BLOUNT Biographies Board at GenConnect under the title "Burke's 'BLOUNT--Barons Mountjoy and Earl of Devon'."

6.  Daniel Kent.  1918.  "The English Home and Ancestry of John Grosvenor of Roxbury, Mass."  New England Historical and Genealogical Register  72: 131-141.  Posted on the BLOUNT Biographies Board at GenConnect under the title "Ursula BLOUNT, one of the 'CROKE' BLOUNTs."