I've just renewed my membership and looked up my original message so I've just picked up your reply! Sorry for the delay!!!!
I still don't know much more about Plas Mariadir but I'll carry on trying. Surprisingly,it still exists but as a retirement home. Looking at your other messages I see you have family from the Stockport area, mine are from Stalybridge so it could be that this home was used for injured WW1 soldiers from the NW.