I am an Australian descendent of the Cornish/Nth Devon Grills (John Walter Grills). I have visited the area several times and my father has information on several branches of the family. Who in particular are you looking for?
I also suggest getting in touch with a Mr Cecil Collocott of Wistaria Cottage, Bradworthy, Holsworthy, Nth Devon. He is somewhat of an expert on the Grills in that area and also those emigrating to Canada and Australia.