Thank you both for your replies.
I have been constantly checking Freecen, to no avail for the whole family together. You have now started me thinking "outside the square". Apart from the Ann and Robert living with another family, I have just found a Janet aged 10 also living with another family. All of these in Barony.
I had previously thought that their parents Robert and Janet McCulloch may have died prior to 1851 census, but maybe they had both died prior to 1841?
Robert's occupation here in Oz was a wood turner and joiner, so this could be him in 1841.
As you suggested, I just did a search on Scotlandspeople, and only one entry for a Robert showed up in Barony - no entries for Ann or Janet within the age ranges (taking into account the 5 year deduction). Mind you, I am not too proficient with that site.
Perhaps if I order in the LDS film for the OPR for Ann's marriage in december 1841, it may show if her father was deceased.

So, thank again. Eventually this brick wall must be broken down, especially with all the records now becoming available.
I often think how wonderful it would be to be able to physically go to the various record depositories to search, rather than from over here in Oz.
Noells