By the way, if you are UK-CV, you can update your Lumia 820 via Nokia Software Recovery Tool (NSRT). Plug in your phone and you should get a screen like this:

If you get a server error or something just try again, or click the 'home' button for the process to restart.
However, installing the update via NSRT will wipe your phone (so make sure you do a back-up, and you're somewhere with a good WiFi connection to re-download your apps!).
The process took less than half-an-hour for me.
Also, don't forget that if you change the region and language settings to English US (you will need to download the US language packs, which will require you going to Languages, adding the US English language and then going to 'Phone Update' which will then download and install the packs) and voila, you have Cortana.
This process might apply to other Lumia 820's that are running WP 8 3051.40000.1347.1006.
So good luck, and whilst this process does mean you'll lose any app data or music/videos/photos stored to your device as well as your tiles layout, it's certainly a lot quicker than waiting for the OTA updates to roll out.


