Hi mm,
No, all my info on Kingswells/Sadleirswells is from internet searches - that site and couple of other hints. Are you or your cousins related to Sadleirs or Massys at all, or were they just living in the house? Shame it got demolished, but when things are too far gone, what else can you do? My other ancestral Irish big house was Blessington House, which is now underneath a brand new shopping centre and dormitory town for Dublin apparently - when I went a few years ago you could still see the landscaping of the grounds, although the building was long gone.
All the best,
Colin in Edinburgh