Hey you! I see the Ravenclaw Trio is finally complete :-p
As for connections, etc...
Agatha: Would likely know him from being a patient at St. Mungo's lol
Justin: Terry certainly knows Justin, no question. And has most likely been hit on/flirted with by Justin (whether Just ever succeeded is up to you). Oh, and of course would have often said hi when Justin was called in to St. Mungo's to check on an injured Ernie.
Percy: Terry would probably know of Percy, but not likely the other way around, but yay for random interactions!
Alicia: May actually know Terry pretty well - she's been trying to work with some healers to see about incorporating her massage into rehabilitation regimens, so they might have seen each other a bit!