Thanks for your replies Cathy and Eadaoin. sorry I haven't been back to this thread for a while.
I've found the site of the Navan Road home on the maps and I think I know where Blackrock is as well now - thank you! There are so many half-uncovered stories around the mother and baby homes aren't there, I hope something will turn up for you Cathy.
For my great-aunt however, I've now found this article in the Royal College of Nursing Archives, about training nurses in Dublin;
http://rcnarchive.rcn.org.uk/data/VOLUME050-1913/page437-volume50-31stmay1913.pdf entitled 'St Patrick's Nurses' Home'
I think this is that place I want, as the article mentions training Queen's Nurses there. If I'm reading it right, this St Patrick's Home was a 'home for nurses', rather than a 'nursing home' so the nurses were based there and went out to work in the community.
It started out in 'the slums around St Patricks Cathedral' and then moved to St Stephen's Green - well even I know where that is

Thanks again for your help

Barbara