Hi Foz ...
Where did you "find" the references to the two Williams and Deborahs?
This will really only be resolved by finding the baptism records of William (jnr.) and Mary. Luckily, the Cumnor baptisms are on Family Search (Batch No. C160771) and there you will find Mary SHERWOOD's baptism in 1814, daughter of William and Deborah, plus some other siblings. William SHERWOOD and Deborah AKERMAN married at Oxford (St. Peter B) on 13 NOV 1803 (Source: OFHS Oxfordshire Marriage Index 1538-1837).
I cannot see a baptism for William BATEMAN (jnr.) in Cumnor, but there is a Joseph BATEMAN baptised in 1818, son of William and Frances. His parents' marriage is not on the OMI, but may be included in the OFHS's North Berkshire MI (which covers those counties originally in Berkshire but transferred into Oxfordshire in the 1970s). Contacting the OFHS for a look up of this marriage may give you further clues to follow regarding William's baptism.
Pennie