Saw Allan's post above about his Telecom Nokia Lumia 059N7B6 notifying him of the available update.
I hadn't received a notification on my 059N7B6, but decided to connect it to my pc, launch zune and check for updates. "An update" (Nokia firmware update 12220) was identified as being available (I had already applied the 2 Windows Phone updates on the 24th july). Downloaded and updated - took 15 minutes.
Now have Internet Sharing (in Settings). Tested and it works very well.
Now have Flip to silence for incoming calls - works well.
So, if you have a 059N7B6, you don't need to wait until you have a notification on the phone, you can connect up to zune and check updates and it should be there.
Just a note to Nokia - the software update availability is still showing as "Waiting for Approval" for the 059N7B6. I would have thought that it should have shown as "Update Available" on the Nokia Website first - this is the place that people are using to check the status of things.
Hopefully all parties have learned something from the process......as a trial run for WP8. I'm not so confident that my WP8 device will be a Nokia - might take a look at HTC or Samsung.