Sommer seems to call this simply White Abbey, apparently as its proper name, one confusing generic.
This is also, seemingly, the same abbey where there was a tomb from which issued such a noise that those who heard it either almost lost their wits or did lose their strength. The monks thought it was a fiend. Galahad, exorcising it, found on opening the tomb that the body was “a false Christian man”. The soul returned, protesting, apparently to Hell, leaving a foul sting, and the monks reburied the body to get it out of the hallowed churchyard.
This incident resembles that at the Abbey of the Burning Tomb, and it is not unlikely that both tales sprang from the same original story, but in the state of the legends today, Phyllis Ann Karr hesitates to recombine them.
The only clue to find in Malory as to this abbey’s whereabouts is that it was about four days from Vagon. That covers quite a territory. Putting Vagon at or near Basingstoke and going strictly by the “minster” or “church” in the name yields possible locations at Kidderminster in Worcestershire, Leominster in Herefordshire, or Church Stratton in Shropshire.