Hi Mandy, welcome to RC.

I think your query might be a bit difficult here, RC has rules about posting information on living, or possibly living, people.
Your theory is sound though, maybe if you post on the Ireland Board with just the family name of your grandmother, someone might be able to help.
Also, you might get results from one of the adoption agencies.
Not being in England myself, I can't help you there, but I'm sure somebody here can steer you in the right direction.
Leonie.