Correct, the ranges at the marker are Bisley ranges.
However, the century range has 108 lanes, of which only about 96 are 600M, 12 are shorter range for specialist competitions.
I know this because I spent 2 (two) weeks (as a part time soldier) repairing and refacing targets every night, and some days during CENTSAAM (CENTral Skill At Arms Meeting) this year.
Competitors from as far afield as Belize, Dubai, Australia all came to compete for four weeks in various disciplines of target and combat shooting.
Site at:
http://www.nra.org.uk/common/asp/general/ranges.asp
History at:
http://www.ewell-probus.org.uk/programme/2005/bisley_ranges.htm