Hi tomoni1,
It's done. The WD40 probably helped.
There was actually no need to remove the button (item 29). I removed it before I went to work but noticed it's not interfering with anything and would have been a pain to re-install because of the spring.
I don't have the override option (item 31), just the cap (31a) so all I had to do was pull the handle straight up with considerable force as you suggested. For anyone with the override option I would guess they would need to disconnect the connector from the bottom before pulling the handle out.
No big deal really.
Many thanks for your help. It gave me the confidence to do it.
Thank you.
Zvika960.