Thank you both for the information!! I really appreciate the time you took to check for me!
Janine - Castle Blunden does belong to my family

It's really more of a Manor House now though. In 1667 Overington (the son of the Overington who is my brick wall) obtained a "grant of Glanmore, alias Clanmore, for the land and Manor House to be forever called Blunden's Castle, and other lands in County Kilkenny, Queens County and County Waterford, by patent dated 19 Feb 20 (1620?). Charles II in 1667." This is as per Charles Mosley, editor, Burke's Peerage, Baronetage & Knightage, 107th edition.
Castle Blunden is still our family seat, so to speak, and the current Baronet of Castle Blunden, Hubert Chisholm Blunden 8th Bart, is my 6th cousin 1x removed. I have photographs of Castle Blunden, but have never had the opportunity to go there myself, I very much want to though. Anyway, to cut a long story short, they will most definitely have information there relevant to what I'm researching, I just need to find contact details for them somewhere

Where did you find the christening and burial info on Overington? That fits with dates I have for him and it very well might be his burial date...