Hi @Yddraig_coc and Welcome to the Forum,,
If you've had the phone from O2 less than 14 days then they will swap it for you.
http://service.o2.co.uk/IQ/SRVS/CGI-BIN/WEBCGI.EXE?New,Kb=Companion,question=ref(User):str(Mobile),C...After performing the recommended fix by the manufacturer without success then you do really have a couple of choices.
Re contact the manufacturer from their Uk Support page.
http://www.sonymobile.com/gb/support/contact-us/Perhaps ring them on ;
Monday to Friday : 08:00 - 20:00
Saturday : 09:00 - 17:00
To call us by phone please call:
0370-5237237
Or you do have the option of O2 repairs as a last resort as we typically suggest a person goes through the manufacturer, as they know their hardware and software better.
Perhaps let us know how you get on.
Take care.