Received this information yesterday December 22, 2010 from direct descendent of Captain Wishart: Lee Watson....
I am getting very close to being able to confirm that the Captain Alexander Wishart husband of Mary McGregor is this man who died in October 1810 in England- this certainly would explain why no one could ever find a death record for him in Scotland:
Edinburgh Monthly Magazine & Review Vol 1 1810 P. 639 Oct. 30 At Exmouth Devonshire Capt. Wishart late of 78th Regiment
and from my own notes for Mary MacGregor Wishart....
Mary's will, first line states she is the "widow of Captain Alexander Wishart late of Her Majesty's Seventy-Eighth Regiment of Foot"....(date beside this statement is May 1847)
Still puzzled by the discrepancy between year of Mary's will (1847) and year of her death recorded at Scotlandspeople as 1843. The numbers in the dates on both applicable pages are very clear.