How peculiar, before tossing it in the bin I thought I'd have one last go. Another 'factory reset' didn't work. However since it still shows up in the utility app I thought I'd have one last look. Right clicking on the 'identify' still made the front LED flash so I thought I'd try sending a factory reset command over the air, which has done the trick. Once updated back to the current firmware version and the various settings re-entered, it appears to be 100% functional, including AirTunes. Bizarre.