Android 4.2.2 Screen Capture on Galaxy Tab 2 10.1
It works out that you just have to keep trying. The Power and Volume down together (for around a second) will eventually yield a screenshot about 1 time out of a hundred. Took a look at most of the apps out there and they either need you to root the device or install loads of other stuff, work for phones rather than tablets or just don't work.

Guess I'm stuck with the crazy combination!