I had bought my Lumia 920 from Phones4U (UK) - SIM free, then found out that it was locked to EE, so unlocked it and I'm on the TescoMobile(O2) contract and as such, the phone still shows EE as provider. But it is under TescoMobile. My OS version is 8.0.9903.10 and Firmware Revision #: 1232.2110.1244.3011
I had only once, had a phone update, but unfortunately, I did not check to see what were the firmware numbers then. However, when I was looking for the Beta version of Nokia "Play To" to download, I found out that the firmware has to be a higher version, i.e. something like 1232.5k... I tried to update mine, but it comes back after checking with "your phone is up to date, checked 2 seconds ago". So I called Phones4U, to see if they know anything about it. The technical help said that they rolled out a new version (which i presume it must have been portico), but they had to roll it back as it has caused signal as well as call cut-offs and freezes. So they are not rolling it out till Nokia releases a fix.
So, according to Phones4U, my phone is up to date! But I am still suffering from heating issues on media playback (super hot!) and also battery life, which lasts about 7-8 hours!
A friend of mine bought his 920 from Vodafone, and his version was 1232.5k.. type, and it worked for good 24 hours on one charge. However, after 4 days he returned it, due to call drop outs and screen freeze on screen pull up on the On-Off screen! So I guess, it is lucky that I'm still on the older firmware! I hope Nokia/MS sort this out quick as the battery is really testing my patience... I am admiring the news of the Galaxy S4 coming out, when I can't do the basic with this one!