Thanks, it confirms what I would have expected:
"Unscrew the retaining collar at the base of the spout.
Remove spout by turning and pulling from the body then
remove old o-rings and replace with the new set."
Problem is that attempting to pull it from the body results in it coming
to what feels like a very solid stop after about a quarter of an inch :-(
I suspect one of the O-rings is a bit mangled and jammed and will need
much brute force. I think I'd better order up a new set of rings before
I try that.
--
Mike Clarke