Hello Ron, and many thanks for your information which was very interesting and useful. I did wonder if Martha Fairweather, daughter to Agnes Langlands, was married to William Sturrock as I have another slight connection with them.
My ggg uncle was James Phillip who married Susan Sturrock on 23 December 1864. Susan was born 1837 to a William Sturrock and Martha Fairweather. James Phillip is the grandson of Agnes Fairweather - Martha Fairweather's sister. So basically, James Phillip married his first cousin once removed (think I've got that right...).
Does this tally with info you have from your wife's line?
I have another Sturrock who I am not sure if he is connected - in 1881 a boarder at the house of James Phillip's brother (Andrew Phillip, my gg grandfather) was a William Sturrock, b abt 1860 in Carmylie... There's a lot of them about!
Back to Alexander Langlands, and a quick search on the IGI brought up an Alexander Langlands born in Tealing in 1738, son to Alexander Langlands and Ann Petrie. Within the realms of possibilty..?
My thanks again, and don't hesitate to contact me if you wish (garen(at)garenewing.co.uk replace (at) with @ - its there so internet spam-spiders don't pick up my email!)