Based on the lugs in the photo, I'd say you were on the right track. It certainly looks like a resonator setup. Premier drums still exists in the UK (according to their site) yet no one seems to be home to answer anything (I've tried, repeatedly).
Guitar Center seems to be the best place to find used Premier kits and they're relatively inexpensive.
Random Premier trivia: Did you know Ringo Starr was a Premier player and only switched to Ludwig because Premier didn't offer an oyster sparkle wrap and that's what he wanted?
Unless he removed the inner smooth shell layer, it is not a Resonator.