At around the same time that my wife & I decided to get membership for Fota Wildlife Park, we also started walking around the grounds of Fota House and Gardens. (Click Here for their site)
Fota House took on its current form in the 1820s when it was remodelled by John Smith. It remained in his family until 1975. It then passed for a while to UCC, and then the Fota Trust.
In 2007 it passed into the care of the Irish Heritage Trust, and they have undertaken extensive restoration work since then.
You do need to pay to enter the house, but a day’s strolling in the grounds is free, and beautiful. (well, you do need to pay €3 for the car park, but consider that helps maintain the grounds)
We spent a lovely day in Fota, give it shot.