I presume that it is a home mortgage you are talking about? You should not change to a non-home mortgage with the Irish Nationwide as they don't pass on interest rate cuts in full to existing customers, they charge penalty interest and they charge early redemption penalties.
There are no penalties on new home mortgages.
If you are moving due to poor service, then you should not move to the Irish Nationwide. Their much vaunted low cost to earnings ratio comes at a big cost in terms of reduced service.
If you are prepared to put up with reduced service, then you have to do the numbers yourself to see if it's worthwhile. The best estimate would be a windfall of around €10,000 in 18 months' time. It is very unlikely that the Irish Nationwide would be the cheapest in terms of interest rates. If your mortgage is €100k, it will probably cost you no more than €500 a year in higher rates. You can probably move again after the demutualisation, so the figures would look something like this:
Windfall: €10,000
Less cost of moving to the Irish Nationwide €1,000
Less cost of moving out again €1,000
Less additional interest over cheapest provider: €1,000
Net benefit: €7,000 for the hassle involved.
If they demutualise before the end of this year, you won't qualify. If the demutualisation is delayed, you will be paying the higher rates for much longer.
Brendan