We know that William married a second time and finding the death/burial of his first wife Mary seems to be a problem. Could this be the missing link:

Deaths Dec 1895
Simmonds Polly 42 Westbury S. 6a 158

Year: 1895
Month: Nov
Day: 24
Surname: SYMONDS
Forenames: Polly
Residence: Park Cottages Lydbrook
Age_at_death: 42 years
Officiating_Minister: H. T. Hoitt Vicar
Event: Burial
Cause_of_death:
Memoranda:
Notes:
Register_Reference: P208 1N 1/12
Page_No: 39
Parish_Chapel: Lydbrook

Mike