The NBI has 1 possible burial for John:
18/4/1804/St.Mary's,Corley,no age given
There's also this one which is possibly his son;
John Pemberton/18/2/1860/St.Thomas's,Keresley aged 68.
Nothing for Elizabeth.
I would advise going to your nearest LDS Family Centre & getting the St.Michael's marriage & birth fiches.
What you need to know from the marriage is:were they married by Banns or Licence,were they "of full age" & are there any Pemberton/Camwell witnesses.
As Camwell is a Coventry name (most Warks Camwells seem to be there) look for Elizabeth on the birth fiches,probably born around 1760-65.
You may have to bear in mind that Elizabeth & John for that matter may have been Christened under another name.
jim