Have you checked the Exeter Cathedral Library?
The other place to enquire IJ is the Devonshire Institution also on Cathedral Green.Barb
I suggest you email both, they may be able to source the information within their archive.Barb ,of course you could visit our beautiful city.
You might find something in the Clergy Database:http://www.theclergydatabase.org.uk/
Are you aware that both the Bishop and his son John have Prerogative Court of Canterbury wills?I have glanced (I stress glanced) through the two wills.If it were my research I would take a hard look at the name LEVERMORE.