I can't help with your specific query
but I can tell you from my experience of other churchyards that there's often no rhyme or reason to where folks are buried - or at least no obvious reason. I'd also say that many graves never had gravestones and those that did have often been removed, or allowed to be grown round and/or are undecipherable.
Some local history societies do maps of graveyards (Loddon in Norfolk has done maps with graves marked) and sometimes a plan of the graveyard might be at the relevant local archives.
You could try writing to the church but I think your best bet would be to try local history/archives sources first.
Chowns in Buckinghamshire
Broad, Eplett & Pope in St Ervan/St Columb Major, Cornwall
Browning & Moore in Cambridge, St Andrew the Less
Emms, Mealing & Purvey in Cotswolds, Gloucestershire
Barnes, Dunt, Gray, Massingham in Norfolk
Higho in London
Matthews & Nash in Whichford, Warwickshire
Smoothy, Willsher in Coggeshall & Chelmsford, Essex