Hi Gidza, I've moved your post into our Note 2 forum, where possibly some of our Samsung experts might be able to assist. Any problems PM me.
It maybe because you've done something that wasn't "official" for an O2 version Samsung, and sometimes manufacturers firmware updates can fail with devices that have been rooted, hacked or modified. The only thing I can suggest myself as I don't have a Note 2, would be a custom ROM, which would bring it up to the latest versions of Android, but it would lose Touchwiz and possibly other Samsung specific features.