Yes Maddie. I think it rules out the Baldock couple.
I am wondering if they might of married in London. I have found the following marriages on Family Search :
William Humphryes & Sarah How at St Katherine Creechurch, London 7th Oct 1783.
William Humphries & Sarah Jasper at St Mary, St Marylebone 5th May 1790.
William Humphries & Sarah Rose Phillips at St Leonard, Shoreditch 16th May 1791.
William Humphreys & Sarah Prockter or Prookler at St Martin in the Fields 21st Aug 1792.
Ravelin