It's been a while since i've updated this but a few more rattles have emerged.
All edges of the lower steering column cover have been covered with the felt tape. Likewise for the arches for the indicator/wiper stalks. Screws done up extra tight.
I still had an intermittent hollow tapping/rattling noise which i thought was coming from inside the cabin but no amount of pounding and thumping could reproduce it.
Turns out it was the cowl cover (the black plastic covers at the bottom of the windscreen). Sections of it had a larger gap between the windscreen and tapping these sections reproduced the noise exactly. The windscreen vibrates a LOT, which is very surprising.
To begin the repair, i cleaned off all the accumulated gunk on the lower edge of the windscreen (and all the area underneath the cowl while i was at it).
I bought some 10mm wide, 3mm thick self adhesive neoprene and stuck it to the bottom edge of the windscreen. The cowl covers were then reinstalled. They were very difficult to reinstall and required some heavy force to put it all back together. I imagine you'd achieve satisfactory results using 2mm thick neoprene but the shop only had 3mm. 3mm is definitely too thick.
This hollow rattle has been completely eliminated
at last!!
I also applied a piece of neoprene to the lower corner of the inside of the windscreen near where the A pillar cover meets. There's a gap there and the cover can rattle against the glass.
The next frontier to conquer will be the sunvisor which has a constant creaking squeaking noise. Tempted to just remove it completely but i will look into less destructive remedies first.