HI Heather
Regarding the issue of spelling variations, it was very much a sign of the times
Spellings were much more fluid in those days and not rigid as they are today. Researching in this period, you have to make use of wildcards where possible to pick up on different spellings of any one surname. As it is, the Snaddon name as you have seen for the family is not too different (one d instead of two; an E at the end instead of an O).
You can see different spellings of a surname on every document that you see!
Regarding the different batch nos. showing on IGI. Batch nos. on IGI are unique to one specific parish. Children showing to Joseph and Janet post the start of official registration 1855 - 1873 look to have been born in 5 different parishes, each one with its own batch no. on IGI.
The list of children showing:
1. ISABELLA SNADDON Birth: 27 JAN 1855 Carnock, Fife
2. JANET SNADDEN Birth: 03 JAN 1857 Airth, Stirling
3. BARBARAH SNADDEN Birth: 03 OCT 1858 Airth, Stirling
4. ISABELLA SNEDDON Birth: 13 JAN 1861 Falkirk, Stirling
5. JANE SNADON Birth: 01 DEC 1862 Clackmannan, Clackmannan
6. JAMES SNADON Birth: 25 NOV 1864 Clackmannan, Clackmannan
7. ROBERT COOK SNADON Birth: 27 OCT 1866 Clackmannan, Clackmannan
8. DAVIDA SNADDONBirth: 07 FEB 1869 Falkirk, Stirling
9. FRANCES MICHIE SNADDONBirth: 22 APR 1871 Tillicoultry, Clackmannan
10. CHARLOTTE SNADDON Birth: 26 JUN 1873 Tillicoultry, Clackmannan
Monica