Thanks to both of you for responding, but I do really want to focus on the question with regard to the Brit basha, not the Australian version at the moment. For one thing, it looks like the Australian version is going for about three times as much. :-)

I have a USGI camo poncho, and an older green one. Decent piece of equipment, but using any poncho for a tarp has drawbacks that prevent me from considering it in less than an emergency- once pitched in the rain, anytime you have to move, to get water, relieve yourself, whatever- you get to choose between soaking yourself or your campsite/gear. IMHO, it's worth the extra couple of pounds to have a dedicated shelter. Emergency bivouacs are, of course, another matter.