I have just come across this discussion and I realise it was six years ago but I'd like to correct some errors.
Marlborough Hall is still there on Mobhi Road, Glasnevin. It is not where Met Eireann is located. It is now the Whitehall College of Further Education. Before that it was where the Dept of Defence finance branch was, called Coláiste Chaoimhín.
Here's a picture of the building:
http://catalogue.nli.ie/Record/vtls000316883 and here is some more information:
https://whitehallcollege.com/from-marlborough-hall-to-whitehall. Two of the buildings on the site are now part of Scoil Móbhí.
I also found my grandfather there in the 1922 Military Census.