Hi Maura
Ulster Bank is the only lender which allows borrowers to apply for a lower LTV mortgage based on repayments and an increase in value.
While AIB will not allow you to move from 3.55% to 3.35%, you should not switch lender as you will not be able to get a better deal. KBC is fractionally cheaper, but they are far worse than AIB in that, even if they reduce rates for new business, they don't pass them on to existing customers.
You could certainly threaten to move, but I doubt if that would influence AIB.
Brendan