Vince,
Happy to help. Preston baptisms for Robinson (no Christiana though) - may be missing, or an error by whoever transcribed these records. I checked all of my 20 villages (only takes a mo), and she isn't mentioned in any of the others either - baptism or marriage. If she was born in Preston, then her parents can't be John & Mary, as they had a son in July 1775.
9 - 1761 MARY ROBINSON D/O WILLIAM/ANN PRESTON
12 AUG 1764 ANN ROBINSON D/O JOHN/ALICE PRESTON
30 JUN 1765 MARY ROBINSON D/O WILLIAM/ELIZABETH PRESTON
10 MAY 1771 MARY ROBINSON D/O EDWARD/MARY PRESTON
5 JUN 1773 HENRY ROBINSON S/O JOHN/MARY PRESTON
11 JUL 1775 JAMES ROBINSON JOHN/ALICE DAUGHTER IN REGISTER PRESTON
7 SEP 1777 SARAH ROBINSON D/O JOHN/ALICE PRESTON
26 DEC 1779 CHRISTOPHER ROBINSON S/O JOHN/ALICE PRESTON
26 DEC 1779 STEPHEN ROBINSON S/O JOHN/ALICE PRESTON
17 NOV 1782 ALICE ROBINSON D/O JOHN/ALICE PRESTON
1 APR 1767? SARAH ROBINSON D/O WILLIAM?/ANN PRESTON
Robinson marriages in Preston:
3 FEB 1760 WILLIAM ROBINSON OTP LABOURER MARY TOMLIN OTP SP PRESTON
? NOV 1764 JOHN ROBINSON OTP SHEPHERD ALICE RUDKIN OTP SP PRESTON
30? NOV 1764 WILLIAM ROBINSON OTP LABOURER ELIZABETH GEORGE OTP SP PRESTON
24 MAY 1812 STEPHEN ROBINSON OTP ELIZABETH CHAPMAN
PRESTON
One burial:
5 SEP 1779 WILLIAM ROBINSON 11 PRESTON
Best of luck

Laura