You are in the unfortunate position of needing a trade up mortgage from your existing lender as no other lender would be prepared to take on the negative equity residual of your existing mortgage. As you say, Halifax are out of the Irish market and AFAIK are not in the business of granting trade-up mortgages. Other posters may have more detailed info on current Halifax approach! In my view it would appear that the only option open to you currently is to rent out your existing apt in time and in the meantime stop overtpaying your mortgage and use the funds saved to build up a nest egg to put towards the purchase of a new home and a new mortgage!