Julie feels dated to me and a little bit downmarket, because it was part of a trend for French names here that started in the late 40s (along with
Suzanne,
Yvonne,
Valerie and quite a few others). It's not a classic, like
Julia. I know a French
Julie in her 20s, though, so I think it might have had a little resurgence over there. I also know an Australian
Julie in her 60s, but weirdly, no British ones at all. Lots of Julias, though, and a couple of Juliets, and a
Juliane, who is Swiss.
Julia is the only one I really like much, but I think
Julie is perfectly usable, and doesn't need to be short for anything.