Keypost is a good reference http://www.askaboutmoney.com/showthread.php?t=168732.
Depending on your LTV PTSB may be cheaper but you want to consider who will be cheaper long term, and that definitely won't be PTSB.
Yea I am trading up but only borrowing what I currently owe on my existing mortgage €180k over 20yrs ... which is only an increase of 3.5yrs compared to the remaining time (16.5yrs) on my existing mortgage .
The balance is coming from savings to bring me up the required purchase amount of €270k approx, which gives me a LTV between the 50%-80% bracket that most lenders use.