Some possible information on Ina:
Birth
20 Apr 1908 Coatbridge
Alexander Joseph Morrison, son of Angus Morrison, spirit salesman, and Margaret (nee Cameron)
Marriage
7 July 1903
Angus Morrison, 32, barman, s John Morrison and Catherine (nee Morrison) deceased
M. Cameron, 28, dressmaker, d, John Cameron, labourer and Catherine (nee Macrae) deceased
Witnesses: Malcolm Morrison and Ina Cameron
1881 census
John Cameron, 32
Catherine Cameron, 33
Mary McRae, 35
Colin Cameron, 11
Malcolm Cameron, 9
Mary Cameron, 7
Margaret Cameron, 5
Alexandrina Cameron, 1 (in 1891 she is Alexina, 12; I haven't found her in 1901, although she may be the 21 year-old servant in Nairn)
I'm not sure that this is your Ina. but the co-incidence of names seems unusual, and this Ina is Alexander's aunt. It seems worth looking for a George Blake/Alex(andr)ina Cameron marriage.
Who is the mother on Ellen Elizabeth Blake's birth certificate?
Richard