Given the potential from rental, the equity you already hold etc. I'd assume the calculators just can't deal with this complex a situation. Really are more aimed towards investment properties/first time buyers and not purchase of a new PPR conversion of PPR to investment.
Again, some of the regulars on AAM are from the mortgage area so should be able to give you some hard facts and figures on this.
Not trying to guide you either way, but a few questions you should probably consider.....
have you owned the current house over five years? (I'm guessing so with the mortgage down to 198k but worth considering for the SD clawbacks etc)
What will the shortfall in the mortgage be after the potential interest rate hikes? (note, might be worth considering the current drop in rental prices around dublin and looking at the potential impact of this too)
What will your finances be like should you fail to rent the property for an extended period?
What impact would a smaller mortgage on the new property have on you? (Quality of life, more disposable income, less stress etc)
Potential savings going for a smaller mortgage? (lower LTV so lower APR, less insurance cover needed, etc)
Just because you recieve advice on something doesn't mean you shouldn't question it yourself and ensure your perfectly happy with your decision.