John HARTLEY, who on the 1851 census states he was born in 1799 at Little Borton, Oxfordshire, this village is a bit of a mystery to me, may be it is the village of Little Bourton near Cropbredy, the spelling in the 1851 census is clearly Little Borton.
Other possibilities are:
The village of Middle Barton has no Church, it uses the churches of Steeple Barton & Westcote Barton. Little Barton was often called Westcote Barton.
A part of Headington, Oxfordshire is called Barton. The Headington area included the three villages of Old Headington, New Headington, and Headington Quarry, as well as Headington Hill, the Marston Road area, Barton, and Sandhills. The parish registers are on the IGI, but no John Hartley there.
I am wondering if he was of the Catholic faith, but when he moved to Hampshire in around 1818 he christened his children in the parish churches at Sherfield English, Hampshire and West Wellow, Wiltshire.
His wife was Sarah, on the 1851 she states she was born 1796 in Bucknell Oxfordshire, I have not found their marriage, or her baptism, the eldest child I have for them is Anna Maria 1819 in Sherfield English Wiltshire.