I've just contacted Olly Europe and they say that the ordinary and ISO(ASA) bracketing work the same way ... 3 & 5 bracketed, require you to depress the shutter 3 or 5 times, or keep it depressed until this number of shots are taken, at which point the bracketing cycle begins again.

If these bracketing modes offered the option of either the photographer pressing the shutter for every exposure OR the camera automatically takes the number of required exposures on a SINGLE depression of the shutter release, this would reduce the risk of getting sequences of bracketed exposures out of sync ... and then discovering the problem when you download and edit the images later on.

Maybe I'm just lazy, but my short-term memory is bad at times and it has caufgt me out when working quickly.