Another one of my probably daft questions! Is there, or has anyone devised a search set to find Fora?
Pardon my ignorance but what/who is Fora? Maybe forums?
Having to a tendency towards pedantry and conscious of the latin roots of the Mother Tongue see the second possible plural from the Shorter Oxford Dictionary:
I see 
I was just confused by the capitalized word. Do you want to find new forums or search in already known forums?
Both! 
If the known forums are indexed by Google/Bing, then you could add them to a search set (see “Sites” tab) and change the mode to “Search”.
Thanks for this. 