Just wondered if your John Garrett and Ann Radcliffe were married @ Maughold 20.02.1787.
I don't have anything more on them at the moment other than they were living in Lezayre when they had their children. I've found 5 children so far one of which I think is the Margaret Garrett who married William Howland [my gx3 grandmother]. Children discovered were John b16.12.1787 Wm b 18.11.1790, Ann b 07.07.1793, Jane b 09.04.1798 and Margaret b 10.07.1801.
I haven't proved the connection yet I need to find some Wills if there are any.
Thought you might be interested.