Does the rent cover the interest on the mortgage, even if it does not cover the repayments?
The montly repayment includes interest and capital. That means that you are reducing the amount of the mortgage outstanding each month by the amount of the capital repayment. Therefore, you are reducing your mortgage which is, itself, a form of saving. You should not be concerned if you are running down your savings to cover the capital repayment element of the mortgage.
Say, you have savings of €25,000 and a mortgage of €100,000.
At the end of the year, you may have reduced the mortgage to say €95,000 but run down your savings to €20,000. Your net borrowings are still the same.
If you talk to PTSB, they would probably be agreeable to your selling the house and converting the deficit to an unsecured loan. However, if you have €25,000 in savings, you would be better off using it to pay off the mortgage shortfall. It makes little sense to have a mortgage of €25,000 at 5% while you are getting, at most, 3% taxable interest on your deposit.
You like the comfort of having cash available to you. But do you really need it? If you are not losing money on your repayments, then you can start rebuilding your nest egg again.
Do you own the house you live in? Do you have a mortgage on that?
For tax reasons, you may be better off repaying the home mortgage first, depending on the interest rate.