Ian,
Yes Annette is correct in that parents names were not given on marriage registrations until 1837.
The parish can also be confusing as it is the parish in which the bride and groom were living is given, rather than the parish in which they were born.
If the Frances I suggested proves to be correct her parents were almost certainly John Twitchett of Ovington and Ann Bland of Belchamp St Paul who married in the brides parish on 14th February 1788.
Belchamp St Paul is only a short distant from Ovingdon.
Mike