Sam pointed me at EMMA, (a Java test coverage tool,) and I've recently found the time to implement it.

Well, it was either that, or struggle with StyleReport Pro. What you you rather do? ;-)

Anyway, EMMA's output is really rather nice. It's structured and informative - you get a good high level overview, but you can you can drill down to reports on individual line coverage. Getting it running with our existing test suite took me a couple of hours of fiddling - but perhaps that's another post...