I have been contacted by Pierre-Maurice Bogaert OSB of the Abbaye de Maredsous, who kindly refers me to a brief discussion of the V&A leaves and cuttings in Revue bénédictine 36 (1924), at p.98.
He also tells me that the scroll held by the woman in the Crucifixion miniature -- which I had read as "Magrite de Matetio(?) Voisia", but which I now see could also be read as "Magrite de Matrtin voisin" -- doubtless refers to Martouzin, approximately 10 miles from Hastière:
There was a Benedictine abbey at Hastière-par-dela, and another very close by at Waulsort, about three miles away, around a bend in the river:
With the re-reading of Marguerite de Martouzin's name, it seems increasingly likely that the house for which the manuscript was made was indeed in the area of Hastière.