Ah, I missed the sterling mention in your first post.
At your LTV you qualify for 3.3% rate with BoI which narrows the gap.
Is BoI rate good value? Not if you can qualify for the KBC rate. But otherwise it's the best long term rate available.
There are a few other options.
First, I assume you've checked with KBC if they would lend on the strength of your income alone?
BoI, AIB and Ulster are the easiest to deal with GBP income.
In terms of 'value', UB 4 year rate at 2.6% is pretty good, and you'd get cash back to cover legal costs. (I'm equating value with margin over interbank rates).
So it's a question of your risk appetite, and how long you want to fix for.