Parnell's full name was "Charles Stewart Parnell". A net-search on that produced a number of good sites including this one, on Avondale - his house in Wicklow, just south of Dublin:

http://www.wicklow.ie/tours/avondale.html

Regards

p.s. Behan appears to have "borrowed" (without attribution), the air of an Orange song called "The Orange Maid of Sligo" (see DT). I always wondered where the air came from - and why you never heard it used for anything else!