Yes - there is some inconsistency but if you want to keep to the traditional historical names it should be Swildon's Seven and Sump VII. See the Swildon's Hole book, Swildon's Hole 100 Years of Exploration, MU5 and the Swildon's Hole surveys.
NB. The passage preceeding Sump VII is Swildon's Seven not Swildon's Six (which is before Sump VI).