You will have paid off about 12k capital during the 2 years - so your outstanding mortgage will be approx 339K .
If you do nothing - PTSB will probably put you on their "standard" variable rate of 5.44 . They have a tracker rate of 5.25 (ECB plus 1.25) - in the short term ask to get put on that while you shop around for better rates.
You could get a rate of 5.05% from Bank of Scotland or 5.1% from AIb IIb or EBS
5.15 from First Active. If you mention moving PTSB might give you a better rate - worth a try.
Halifax have a discount offer of 4.55 for 1 yr then 5.1% (ecb plus 1.1) after that.
You will have legal and valuation fees if you move - some lenders will pay towards these. Halifax give 1000 towards legals and refund the valuation if you switch.
If the value of your house is more than 425k (i.e your LTV is less than 80%) as per the best buys - you will get the best tracker rate from NIB on their "LTV Mortgage"