Although not directly relating to custody, this thread is an interesting discussion to the situation of the time.
Worth trying the National Archives for records.
The thread I`ve linked to suggests any divorce of that time would be held at the high court.
Interesting reading, hope it helps.
http://www.rootschat.com/forum/index.php?topic=258715.0

This link to the National Archives may prove useful
http://www.nationalarchives.gov.uk/records/looking-for-perso...