I don't suppose you've ever visited Luxulyan but I can assure you that it's a very pretty part of Cornwall, with small wooded valleys and the ancient stone viaduct which carried a railway. Cornwall is the most beautiful county and Luxulyan is near the sea. Unfortunately though, it's economically depressed since the old industries of fishing and mining are no more.
My grandmother was born Maud Grose in September 1874 in the village of Roche, an upland clay (Kaolin) mining village only five miles from Luxulyan. Her father, Nicholas, owned and ran the village shop. I have always understood that the family came from Luxulyan and one of my brothers remembers as a child being shown a picture of the family home. However I believe you may be mistaken in supposing that the Groses originated there since it is a common and an old name in Cornwall, and is also found elsewhere in the UK. Maybe it developed from the French word 'gros' meaning fat, and they came over with the Norman Conquest in 1066!
Ten years ago I devoted some time to searching family history, but I've moved house three times since then and have mislaid my documents, unfortunately. Because the name is common thereabouts I found it difficult to research - for instance two Anne Groses were married in Roche in the same year and I didn't know which was which.
Two of my mother's cousins survive, aged 93 and 87, and the women of the family all seem to have been feisty (bossy) characters. The affection for Cornwall remains strong in the Grose descendents.
I'd be interested to know the dates of 'your' Nicholas. Someday I shall have to research all this properly, but I don't think I'll have time before retirement...