Hi Gadget,
It all adds up! Wonderful! Thank you

I've had a look at Scotland's People & it all fits nicely. I just can't find any Death Records for any of the Alexander JOHNSTON's, Barbara JOHNSTON (nee LEYS), or Elizabeth JOHNSTON (nee WALKER).

Alexander JOHNSTON & Barbara LEYS Marriage in 1805 states that her Father is an Alexander LEYS (Farmer), though the only Barbara LEYS born to an Alexander LEYS I can find was in 1805 (which doesn't fit the time frame at all). I can't reconcile the 1783 Barbara LEYS d/o James LEYS and Margaret FARQUHARSON (the dates all add up here though) with the Marriage Record? If I could find a Death Record for Barbara JOHNSTON, I could sort that out.
Alexander JOHNSTON & Wife Elizabeth JOHNSTON (nee WALKER) have disappeared again, after the 1851 Census...They are all over the place, aren't they!
Thanks for all of your help - it's been so wonderful to finally be getting somewhere

Cheers,
Nikkii