Thanks so much ev, and many apologies for my delay in acknowledging your sterling efforts, greatly appreciated! I can only put it down to 'A Seniors Moment', and my confusion about understanding that the whole family must have returned to Scotland.
At least it means I can stop looking for any of them in Australia!
Have you any advice about how I find out if Robert Snr, who would have been about 44 at the time he pops up on the 1861 Census, would have got his army pension when he returned to Perth from Hobart, or would he have to wait until age 65 or something? I'm intrigued that in his letter of 1845 he mentions earning 9 pence a day, and has a wife and 2 children, and by 1856, with 5 children, he's still in the army, but he's managed to send his brother 100 pounds!