I think this is the burial of the Ann Lockwood you found.
Ann Lockwood aged 40yrs,of Sandbeck, buried at Letwell 1 February 1863.
(Letwell is not far from Dinnington).
Henry Lockwood Machin, bap 30 Sep 1873 at St. Simon, Eyre St.
Mother - Sarah of 10 court Porter Street.
Is it possible that Ann Lockwood died after giving birth to John and that John was not baptised until the following year? The six year gap seem rather a long time between John baptised in 1864 and Henry Lockwood Machin born in 1870.