I know avm228 said they'd go, but as I was nearby late on Sunday afternoon, I had a look. There are two St Mary's, both listed in the book. The second one, with the map, is St Mary Magdalene, between Furlough Road and Madras Road off Holloway Road. Of the 90-odd gravestones and table tombs listed in the book, I counted about 30. I might have found more, but it was getting dark. Maybe I'll go back another time for a longer investigation in daylight with the book in hand. Many of the inscriptions noted in 1951 are now illegible, and I'm not very hopeful that the Irish's tomb can be identified now if it wasn't in 1951 (and if this is the right St Mary's).
The other church, St Mary the Virgin and presumably the first in the book, is not far away in Upper Street just south of Cross Street. (My grandparents were married in Cross St Chapel, but it looks as if it's been rebuilt since.) This St Mary's churchyard is a lot smaller than the above. There are a few table tombs and some gravestones propped along the side walls, but it was by now too dark to make out any names. The few flash photos I took suggest they are also all eroded.
Sorry for not better news.
FOOTNOTE re St Mary Magdalene.
Names I could make out:-
Thorne
Williams, Burton
Hartley
Purdy C.7
Fletcher E.3
Smith E.4
Collins?, Glover
Watkinson D.1
Walkden, Skeggs D.3
Sabine, Piffard H.23
Costar, Wigan H.12
Bentley H.8
Smith H.6
Line?
Gee, Phillips H.27
Fredericks?
and a footstone with initials and dates only which I leave as a challenge:
E S 1836? / M M W 1810 / M W 1811 / E C 1812 / J C 1817 / J S 1847 / M M S 1848
The noticeboard gives a little history:
The gardens of St Mary Magdalene Church
were originally burial grounds laid out
around an early Victorian Neoclasical
Chapel of Ease. The 19th century
Coroner's Court and Mortuary occupy
the south-eastern corner of the grounds
which closed for burials in 1856. The
churchyard was re-ordered and opened
to the public in the 1890's...