Hi again Foz - a few more bits of info:
Can't find anything yet on the 1881 census discs. So went to scotlandspeople again and searched the 1871 census for a John Hairstens. Found only one relevant one (for the cost of only one credit again). For another 5 credits, you could view the full census page online.
This was John Hairstens, age 13, at Troqueer, Kirkcudbrightshire - very close to Dumfries.
Went then to Ancestry and checked the 1861 census for an approx 3 year old John Hairstens (or variation on the spelling!), and found what is almost certainly him with his family as follows:
Living at 39 Church Street, Troqueer, Kirkcudbrightshire
Burgas Hairstone (cracking name - love it!), age 43, Gardner, b. Troqueer, Kirkcudbrightshire
Mary Hairstone, age 32, wife, b. Sanquhar, Dumfrieshire
Mary Hairstone, age 20, daughter, factory worker, b. Troqueer, Kirkcudbrightshire (so looks like Mary above is Burgas' 2nd wife)
John Hairstone, age 3, b. Troqueer, Kirkcudbrightshire
Jane Clark, age 30, sister in law, (forgot to note down her place of birth, but think it was Sanquhar also - will recheck).
So looks like Mary Hairstone is nee Clark, which fits nicely with John Clark Hairstone/Hairstens' middle name and makes it fairly certain this is the right family.
Hope this is of some help in getting you going. No luck with Jane's side yet, but I'll keep trying.
Cheers
Ellen.