Just an update on this issue, and opinions as well if possible!
I lodged a complaint with AIB over this which they said was investigated, I got a letter saying there was no fault on their side and Tesco was to blame for not accepting the cheques from them.
So, I left it and tbh forgot about it - until couple of weeks ago I received 2 letters from an post within a few days of each other. Both contained the balance transfer cheques issued by AIB - and sent to the wrong Tesco address. Now the customer service people from Tesco said to make sure AIB sent to the correct address - and I did raise this issue with AIB who insisted that they could not have got it wrong. But they did, and I have the proof now down to the wrongly address envelopes!
So basically I would still like to avail of their 3.4% balance transfer rate. I am trying hard to pay down my tesco cc but its taking ages because of the high interest I am being charged. However, this rate runs out in Nov 2013. I would accept, as an 'apology' from AIB if they extended this for another 12 months so I could get the balance transfer through, since it was their incompetence that failed me in the first place. I intend to write to the ombudsman and AIB regarding this and include photocopies of the cheques and the misaddressed envelopes. Does anyone think I could achieve this outcome?