It says the baseband is stock 77? I went to settings & 'About phone' to check this.
In brief, I had my phone network unlocked and BL unlocked by Wotanserver. I'd been under the impression that the DRM keys were ok (e.g. Trackid and Timescape still worked afterwards). Anyway, I attempted an FOTA update and bricked it. I used s1tool to 'restore' and then an ftf I found on xda developers to relock the BL, flashed a stock ICS .587 ftf and got the phone 'working' again - except for the SIM not being recognised. Aside from that, the phone seems ok.. though I have noticed that every time it boots it immediately asks me to select a language and it won't let me save the standard VPN settings I twice tried to input manually. PC Companion and SEUS haven't helped, and I also noticed that in the Flashtool log there was a blue line saying 'this file is ignored simlock.ta'.
Anyway, after spending hours trying to find a solution something somebody said on a thread seemed to ring true in my case; i.e. that the Simlock Partiton is damaged and that I need to 'resign' it, and this can only be done by Sony or by pay Servers on the internet. Does that make sense?