David Bewes explains: (many thanks)

There are several versions.

• Either: (Heralds College 18 January 1913):
  • Arms: Azure, a fesse flory counterflory between three unicorns' heads erased or.
  • Crest: On a wreath of the colours, a demi-unicorn supporting between the legs a sceptre erect, all gold.
  • Mantling: Azure and or.
  • Motto: "Le Lierrelie longs liens"
• Or: those more anciently in use in our branch of the family, & in use certainly since before the end of the 17th Century on most of the memorials in the church at Ditcheat and Charlton Musgrove, & in the 1830's on family silver:
  • Arms: Azure, a fesse raguly between three unicorns' heads erased or, as many flaunches of the last.
  • Crest: On a wreath of the colours, a demi-unicorn supporting between the legs a staff raguly erect, all or.
• Another version: (see WILKINS-LEIR in Fox-Davies' "Armorial families"):
  • Arms: Azure, a fesse raguly between two unicorns' heads couped or, as many flaunches of the last.
  • Crest: On a wreath of the colours, a unicorn's head couped or, in front of a saltire raguly azure.

Notes: "Azure" (ie the shield colour is blue, tending towards cyan), "a fesse raguly" (a fesse is a horizontal band across the width of the shield at the mid-point, raguly means that the edges of the fesse are like italicised battlements) between three unicorns' heads "erased or", ("erased" means that the head is torn at the neck in a jagged way, as opposed to "couped" which means cut with a clean line. "Or" means that the heads are of a golden colour). "as many flaunches of the last" is puzzling as no flaunch is shown on the arms. A flaunch is a semi-circular area normally on either side of the shield.
Crest: On a wreath of the colours, a demi-unicorn supporting a sceptre (or staff) "raguly erect" (ie the sceptre is vertical and the edges are "raguly" (ie like italicised battlements), Or (meaning of a gold colour).

Motto: "Le Lierrelie longs liens" is obviously a play on words. "Lier" (a variation of the name "Leir") is a French verb meaning to bind, tie, or unite. "relier" is a closely related French verb meaning to link, join up, connect etc. "lierre" is French for Ivy. "longs" means long. "lien" means bonds, links, connections, attach etc. "Lierrelie" should probably be broken as "Lierre lie". So the motto might mean "The ivy binds long bonds" or "the Leirs bind together long-standing connections".