Hi Maggie, I think I found them on the 1841 census in Dundee, which shows they were both born in Angus, and has ages, which may narrow it down a bit.
Piece: SCT1841/282 Place: Dundee-Angus Enumeration District: 70
Civil Parish: Dundee Ecclesiastical Parish, Village or Island: -
Folio: 0 Page: 19
Address: Dalfield Walk
~~~~~~~~
Surname First name(s) Sex Age Occupation Where Born Remarks
SHARP Jas M 27 At Steam Looms Angus
SHARP Ann F 20 Angus
SHARP Jas M 1 Angus
I noticed that they had 3 kids in Dundee
James 30 Jun 1840
Mary 16 Oct 1845
James Lyell Sharp 30 Jul 1848
I found a James Sharp b1814 in St Vigeans and an Hannah Lyall in Carmyllie in 1821. The two places are very close. There is also an Ann Lyall in Dundee 1819.
Good luck
Lesley