To follow up on my earlier post, the curious thing, though, is that whilst I can't get TIME /S to work at all on some timeservers, it still seems to be working more-or-less flawlessly on others e.g. NIST e.g.
nist1-ny.ustiming.org
and on a few UK timeservers that I've tried e.g.
ntp.demon.co.uk...