Ouch that was a painfully long delay...
The pause in committing code was because I hit an issue between DataAction and Play that took a little while to resolve. So there's a commit on the handy project that's just been pushed to resolve it.
The gory details can wait for another time, but the short version is that Play has a distinction between
Action, and these two Play classes don't work quite as nicely together as I naively assumed. This was causing problems in
DataAction.one(parse.json). It was a bit of a fiddly workaround that was needed.
So, back to it, but having taken a few hours out to deal with that, I might be having a late night after all.