Hi Rory,
It probably would be best to ask the local parish priest to view the records and work your way back from your grandparents.
Parish records can sometimes be very detailed...or it might just record the names and the date. But for the 20th Century the records should be quite detailed.
From your grandparents marriage you should get what townland/street they lived on and hopefully who their parents were. Although most marriages only lists the fathers name and not the mothers.
Also from their marriage you should get a good idea of when they where born and you can look back through the records for their births, parenst marriage and siblings briths.
When where your grandparents married approximately?
Hope that helps.
