I've also been looking for Gatens/Gattens ancestors. My information is that Philip Gatens and his son Hugh lived at Limavady, Derry in 1831. Limavady is only about 10 miles as the crow flies from Moville so there is a good chance they are related. Hugh emigrated to London in the 1830s and I have now traced all of my branch of the family that are descended from him. If you find any more about the Gatens from Ulster I would love to hear about them.
Cheers, egaten