Sorry missed your reply, didn't have auto-subscription on.
Rifle is an HW100. Not a problem other people knowing; it's a matter of record on other fora.
Using a cotton bud I've now removed most of the excess grease from the trigger, cocking arm and shuttle. It does seem a little more consistent now. Still sensitive but after experimentation I've been using the 9 degree clicks at every NEFTA WL since November in spite of it being a fair bit colder at one or two shoots.
So I suspect instead of being an almost linear relationship as it seemed to be, it now seems to "cluster" around two points.
Now the WL is finished I'm minded to strip it, degrease and run it nearly dry (using dri-slide and a tiny smear of LT2). It will be an interesting exercise.