Dorrie, many thanks for the certificate. While not the right Margaret Caldwell, it does help to eliminate her from my search. Thanks also, Monica, for details of the Leitch family - sadly, not mine.
My Margaret Caldwell (sometimes Coldwells) is proving very elusive. I've searched on SP, Ancestry, FindMyPast and FamilySearch without success.
In the 1851 census she was Margaret Caldwell, unmarried, house servant, aged 65, born Dalkeith, living in Duddingston.
In the 1841 census she was Margaret Coldwells, servant, age 52, born Midlothian, living in Dalkeith.
I couldn't find her in 1861, so it seemed likely that she died between 1851 and 1861.
I found a possible baptism for a Margaret Coldwells on 31 August 1785 Dalkeith to John Coldwells and Alison Sanderson but was able to eliminate this one as she appears in the 1851 census in Stobsmills as Mrs Margt Philp with her brother John and mother Mrs Alison Coldwell.
I do have the certificate for the unknown Coldwalls who was buried on 8 June 1851 in Dalkeith:
Widow Coldwalls, residence and parish Musselburgh, Order gotten by George Watson, relation a friend, cause Paliaze? 60 years
but this seems unlikely as she was married and died in Dalkeith only a few months after the 1851 census entry.
Thanks again everyone for your feedback - I think this one goes back in the "too hard" basket!
Jan