Hi Ugo
Have you tried checking for the family in censuses? Often a useful place to start for information and dates. IGI is a great resource, but where you have entries showing as submitted member entries, you need to take some care as you know until you are able to verify elsewhere.
If I have the right family in the censuses, I think the marriage between John Lander and Mary Currie is probably earlier c. 1840.
I think this might be them in 1861:
John Lander 47, Joiner (master) b. Edinburgh
Mary Lander 43 b. England
Isabella Lander 16 b. Edinburgh
John Lander 9 b. Edinburgh
Jane M Lander 6 b. Portobello, Midlothian
Thomas Mungal 1 boarder b. Edinburgh
Address: 2 Ramsay Lane, Portobello, Duddingston, Midlothian
You can find the family on the 1851 census on
http://freecen.rootsweb.com/cgi/search.pl - just search for John LAUDER in Midlothian, occupation hotel keeper.
Can't easily see the family in 1841.
If Mary Currie died in Scotland, her death cert should include full details on her parents, including mother's maiden name. There is a submitted entry for her on IGI:
Mary Curry chr. 29 Oct. 1810 in Kirkwhelpington, Northumberland, England
Death on 4 Feb. 1870
Marriage to John Lauder c. 1840 in Edinburgh
Something to work from

Monica