Hi there,
I've done some digging around and he's probably buried in the cathedral -- not an unusual thing.
I can't seem to find a floor plan that lists who is buried where but, since you are going there, they probably sell a much more thorough map of the building that would include his spot. Also, the contacts I've listed below can probably assist you with this.
This is the official website for Salisbury Cathedral: http://www.salisburycathedral.org.uk/
I looked through the site and found a contact for you. Depending on how soon your trip is, you might just want to call them. Since your relative was John Jewel and he was a bishop at the cathedral, it's likely that all the relatives (at least somewhat close by) went there to be married, buried, and baptised.
Contact: Wiltshire & Swindon Record Office Tel: 01225 713138 (Archivist Room).Salisbury Library 01722 330606The Cathedral Library only holds records of people baptised, married or buried in the Cathedral.
There is a button for a contact list on the home page. There are a few other possibilities there -- the Canon Chancellor (who oversees the visitors center), the librarian, and the Head of Visitors Services. Two of those have email addresses.
I found another link for family histories there: http://www.salisburycathedral.org.uk/history.family.php This link also has a couple other links to "useful family records" websites based in the UK.
Another place to try to track down some relatives is: http://www.familysearch.org/
They are very thorough and usually have pretty up to date records -- so you can get living and dead.
I really think speaking with people at the church is going to be your best bet. When I was in Scotland, there were several church ladies that knew EVERYTHING about their church's history and families (past and present). It was amazing how much they knew!
Best of luck on your ancestor search. I hope you have a wonderful trip to England.
Hope this helps,
Heather
Office Manager & Researcher
I promise to answer your questions honestly and correctly. I love helping people.