Yes, the church office is at the Old School. Open weekday mornings.
There are no Samuel Lewry entries in the Bolney registers up to 1812. However there does seem to be one which says child of "Thomas and Mary Field or Lewry". William baptised in 1809, Oct 15. Is that your connection?
Searched Cuckfield baptisms starting from 1780 to 87 and there isn't a child of Mary Field then. Though they are hard to read.
There is one for James and Mary Field. Thomas bap 31 Aug 1788.
No Lewry entries at all.
Have you tried Slaugham? A lot of Cuckfield folk were baptised there.
Andrea