Hi Austen,
I've looked through the parish registers of Bluntisham, St Mary's and only found two references to Leedens.
John Stacey bac married Elizabeth Leeden sp botp. 28 Feb 1832.
Wits. William Benington, Bathsheba Lavender.
Elizabeth Leeden adult dau of John and Elizabeth of Houghton, lab, now the wife of John Stacey, yeoman was baptised 1 July 1838.
Can't help with other parishes I'm afraid. If you want the children of John and Elizabeth, let me know

Tempsford.