1. You have to realise in this situation is that your downside risk is to have to pay the commercial mortgage back yourself in full. Under Irish law, there is no such thing as handing back the keys and then not having to pay the mortgage. The bank (NIB/Danske) can follow each of you individually for the full amount of the mortgage, including for any shortfall if the mortgage is sold. Accordingly, at this stage your best option is to seek the sale of the property (this will not take 18 months,more like six) or else to reach some agreement with your co-owner to buy out his share. Essentially, as long as the mortgage goes unpaid, your partner is really only increasing your potential loss, as the bank can look to whichever of you had money to pay the mortgage. The bank can get the full amount from one of you. IN the case where you are the financially solvent partner, this means that you are the person to whom the bank will look to, for recovery.

2. Be aware that any shortfall when the property is sold will continue to be recoverable from whichever of you is the solvent person. Accordingly, you don't have the option of handing back the keys and letting the bank take the property. You have to find some other way out of the conundrum.

3. The fact you live in the UK is not a bargaining chip. An Irish bank views a legal action for recovery in the UK as meat and drink. It would be different if you were living in Uzbekistan or somewhere like that. Secondly, debts are often sold to debt collector. It depends on whether the bank takes the view it can recover the money or not themselves and easily. However, Danske BAnk who own NIB have a hard assed view of debt recovery. They will first attempt to recover it. However, Danes are very pragmatic people. If they will get value from selling the debt they will do that. Of all the banks, they are one of the least user friendly and will not flinch from pursuing you. Remember, in Denmark they have one of the lowest delinquent rates of all.