It's all O2
I have had several times got a Sony/Sony Ericsson/Ericsson with O2's version, and also other network providers, and as soon as you get rid of this, the phone works fine, may be a tweak or two, uninstall some items from the generic uk firmware for the phone.
I have also found that some times, if there is a update, just go to update the phone if you know a new version of firmware is out, as it appears that even if you have not had the notifiy me that there is a update, it never gets acknowledge on the phone, almost as if something has blocked this???
For a example, had a X10i, no notifications, but going to XDA-Developers and also SE web site (At the time) saying that there is a update, used the update service, went through the first few steps of checking with the servers for new versions, and suprise there is a update, even though no notification from the over air notification and the normal desktop PC Companion.
Also helps to have unlocked rootable phone, which is a problem I am having with my Xperia S, teach me to get the phone from O2.. Will resolve this one way or another