Well, Brendan takes the view that nobody should fix for a period of over 1 year at any rate above 3%.
If I was in your position, I would look at switching to a better variable rate with another lender (KBC offer an effective variable rate of 3.6% at your LTV and will meet all switching costs). But if I couldn't switch for some reason, I would be strongly tempted to take the 2-year fix with BOI.
I would definitely takes steps to move off your current 4.5% rate as a matter of urgency.