If you are looking for a British job,then your UK credit rating is fine.
Honestly (from experience) AIB are not good to deal with.They are intransigent and unwilling to do a deal of any kind.
I kind of expected a response like you just got.
If you never answer the phone,because AIBs number is blocked,for example,then they would have to deal with you by letter.
Eventually(up to a year) they would appoint BCW ,Stubbs or one of the other agencies .They will then write to you .Many times.They will ring you,if their numbers aren't blocked.
If you don't engage at all,the debt collection agency will lose interest.Possibly a second or third agency will be appointed.
They will all threaten court.But that's all it is.Empty threats.There is no percentage whatsoever in taking someone who is penniless to court.
They might then (in about 2 to 3 years) offer a settlement of 50%.
Please note that if you accept,you reset the clock on the six years enforceability of the debt .The debt stays on your ICB record for 5 years after you have cleared the debt,or its written off .
So,say in 3 years,you accept a 50% settlement of your debt payable over 3 years,then your ICB won't be clear until 2028 .
Unfortunately trying to do the right thing has more disadvantages than advantages.
It is up to you how to proceed,but keep some of the above points in mind.