Windscreen demist ducting
I probably mentioned before the slow demist and de-ice airflow to the screen. Although the little heater matrix warms up very fast, and the fan blows quite vigorously, when I closed the dashboard vents and the (repaired) lower outlet door, there seemed to be a real lack of air coming up under the glass. Could hardly feel it in fact.
I'd been told the air could be escaping underneath the top of the dash, where the heater duct points upward into it. I investigated this from inside the engine bay, where I could just reach the front side. I could also get a finger or two UP the duct from inside the car when I took the dash off to repair the wiring. The top flap was opening properly, so it wasn't that. The heater fitted into the under-dash fairly well, though not exactly airtight. I pushed the surrounding plastic down as best I could from inside and smeared some sealant on the join where I could get to , which wasn't a lot.
Then I looked at the heater control panel on the dashboard, since the foam plastic I re-glued last time didn't look to be a good fit. In fact it was a very bad fit!
The heater front outlet is rectangular. The panel and flap are rounded, smaller, and angled so there is quite a gap at the bottom. I stuck in some thicker foam to make up the gap:
You can see how much thinner the original foam was.
Look at the hit-and-miss fit...
Anyway, I could see the flap would hit the new foam, took 2 tries to get it right:
With the dash off I could refit nearly all of the panel (and those T20 screws) :
The only real fiddly bit I found was clipping the control wires back mostly by feel - these little things:
One other job I did was put some more glue on the cracked castellated bit of the temperature knob. It was slightly loose as I was cautious with the superglue last time.
Lots more air comes out of the windscreen slots now 
Though as it has been an unusually dry and warm September I can't see how effective it all is.
PS - October, colder and damper, and the demist function is much improved :-D
Aixam