Hi there,
Im no professional but I am in a similar situation. We have just completed the purchase of our site and we used PTSB for a remortgage on two existing properties, enabling us to pay for the site. They were by far the bext with rates and deal but we did go through a broker which I found much better! For the new mortgage which will finance the actual build, like yourself, we also went with them and got a great rate and they do stage payments. BOI came in second but beware of BOS - they dont so stage payments. Probs no help but thats our experience!