Hey. As in a a greeting. Hey guys. Hey gang Or simply Hey.
I know it's been around for a few years now - no doubt inspired by creeping Americanisms in British English. I also realise that "Hi" was originally American and which I have no problem with and actually use myself regularly. Which demonstrates my own inconsistencies I guess. 😄
But Hey still grates. It feels to me more like a slightly impolite hailing for someone's attention than a friendly greeting.