If someone had enough equity in a house in Northern Ireland to withdraw equity and purchase a property in the Republic of Ireland, what interest-related expenses would be tax detuctible and how would the exchange rates work?
My guess is that it'd be 75% of the interest, just like with a mortgage sourced in the Republic of Ireland, and that the interest should be calculated based on the exchange rate on the days in which it was added to your mortgage.
The reason I ask is that, if this were a viable option, there are 2.79% 5-year fixed rates available in the North. The person in question is living in the North and earning enough to pay the mortgage without any of the rental income so difficulty with regards to fluctations in the sterling obtainable with the euro rent on a monthly basis wouldn't be of a concern.