In message , at 21:32:31 on Sun, 29
Jul 2012, stuart noble remarked:

Normally, taking the top half out is a pain. The inner sash is normally
the bottom one, and this is only held in place by the staff bead. No
chopping necessary, the bead just prises off. Also no need to touch the
parting bead.

The lower one is the inner one, but there are three substantial beads
holding it in, and as it's immovable maybe more than just the paint
fixing it there as well.

I'm becoming more optimistic about being able to open it half a pane,
and then use some sort of angled brush.
--
Roland Perry