Hi Foz,
I found possible births recorded in Liberton, Midlothian for Robert Trench and his siblings (British Vital Records CD's) to parents Robert Trinch (Trench) & Elspeth Cook
TRINCH, Margaret, Born 16 Apr 1834, Christened 1 Feb 1835
TRENCH, John, Born 30 Dec 1835
TRENCH, Daniel Ritchie, Born 23 Mar 1838, Christened 22 Apr 1838
TRENCH, Robert, Born 7 Jun 1840, Christened 21 Jun 1840
TRENCH, Walter Kay , Born 14 Feb 1843, Christened 12 Mar 1843
There were rather more possibilites for Elspeth Cook (presuming she was born in Midlothian around the same time)
COOK, Elisabeth, Born 26 Mar 1839, Christened 28 Apr 1839
Recorded in: Lasswade, Midlothian
Father: David COOK Mother: Margaret MUIR
COOK, Elizabeth, Born 23 Sep 1844, Christened 18 Oct 1844
Recorded in: Edinburgh, Midlothian
Father: Alexander Shank COOK Mother: Jane STIRLING
COOK, Elizabeth, Born 19 Sep 1844, Christened 30 Sep 1844
Recorded in: Edinburgh, Midlothian (Collection: St Cuthbert)
Father: James COOK Mother: Elizabeth SIMPSON
COOK, Elizabeth, Born 29 Nov 1845
Birthplace: Corstorphine, Midlothian, Recorded in: Corstorphine, Midlothian.
Father: John COOK Mother: Christina HARROWER
Of course none of the above might be your Robert & Elspeth!
Anne
P.S. Leith (their place of marriage) is in Midlothian, not Stirlingshire