Rebuilding credit score & cleaning files

I sent all my letters to the Data Controllers at the set addresses as per cleaning your credit file sticky over 3 months ago. I am left with 1) a Nationwide account still as default with no ammendments at all, 2) a Nationwide account that belongs to my xh that has nothing to do with me which my local branch has confirmed showing a default for which Nationwide have failed to respond at all or to remove me from that account (that one is abysmal of Nationwide as that should be private and confidential to my xh and I shouldn't be able to see how much debt he obviously is in), 3) a Natwest account also showing default and no ammendments and 4) 1st credit also showing default with no ammendments.

So that is 4 accounts I need to complain to the Information Commissioner about. This bit seems a pain in the neck! I did send everything recorded and know my letters got there as I checked online so I now need to print off evidence my letters arrived there from the online site, print off my original letters, and now send that to the Information Commissioner?

Also, on my other closed and settled accounts, some of the default dates are after the BR date, some are recent dates. Is this worth bothering about? If it is worth bothering about, I guess I try again with these companies to get them to ammend the dates rather than complain about them to the ICO? I say that, because apart from default dates, they have at least marked the account as settled/satisfied and marked the accounts closed.

On a more positive note, one of the things I emotionally struggled with when I went BR was Next, to whom I have never owed a penny and always paid my bill in full every single month reduced my credit limit from £3600 to nothing so I have had to pay at the point of ordering each time. Today, my credit limit is now £3000. Almost back to where I started! I will still always pay it off every month as I do all my bills, but it does make like easier and makes me feel better emotionally. I am wondering if I will soon being able to get a sim only deal for my phone in my name, at the moment my sim card is in my daughters name which is a pain. Small steps but nevertheless steps.