Hi Scrambled Egg
Not sure who the best person is to speak to.
Did you get the name of very helpful lady who told you that you should have been offered the tracker rate. While she may have been friendly, I am not sure that she was helpful. She should have initiated the correction herself.
1) Tell them to put you on the correct tracker rate immediately
2) Tell them that you want to be put on the tracker rate from mid 2009.
3) That you want a cheque for the overcharge. They may well say "We overcharged you by €10,000 and we have reduced your balance accordingly". This is not acceptable. They must give you the refund.
4) If you have had higher rate borrowings elsewhere or if the much higher payments have caused you distress, you might claim for that as well. I don't think you will succeed, but claim it anyway.
5) If you have missed repayments and had your credit record damaged, then you will have further complaints to make
6) In your letter, you should outline the calls you have made and the lack of help from ICS. (This might be useful if you have to go to the Ombudsman, which I don't think you will)
Then wait and see how they respond.
They will probably tell you that you chose a fixed rate from 2009 to 2012 and so they won't be giving you a refund for that period. If they do that, let us know and we should be able to find an Ombudsman's ruling on that issue.
When you get sorted, please make sure to post an update here. I think you should consider raising the issue with the Central Bank, as this is probably a systemic mistake and ICS should have picked this up themselves. But don't do this until you get sorted.
Brendan