UPDATE:
Within less than 7 days from first discovering this issue, O2 have removed the default from both of my Equifax and Experian Credit reports.
As discussed above I informed them that the data did not seem accurate on their systems. They claimed that I'd missed payments when I hadn't and that letters were sent trying to collect the debt after the default was put on. However I never received any of these letters which were apparently sent. For this reason I asked them to send copies of all paper corrispondence that was sent to my home address.
I got this in their reply:
"With regards to letters, the system only logs when each letter (or each type of letter) is sent. The only thing I can give you is example templates used within standard practice."
As you can imagine this provides no evidence that these letters were ever sent.
Although I am pleased I have managed to get the Default removed I have spent a lot of time, money and suffered plenty of embarrasment because of O2 and their heavy handed tactics. I am likely to push further to gain additional compensation especially as I am suffering to get on the property ladder because of this.
Joe Burns
Joe Burns