Car runs great with 60,000 miles on it, however, there is a continuous tapping noise coming from the motor?? I have been told that it may be the original tentioners? Is this common?

 

From what I read around here, yes it is. Check out the XJ8 section FAQ I am sure that you will find more info.

 

Do you have the repair history? Have the original tensioners been replaced by the updated 3rd generation tensioners? If not, then I would recommend having yourself or a mechanic pull off the valve covers on both sides of the engine and check to see if the plastic upper secondary tensioners have failed or have cracked (about to fail). Even if they are ok now. If they have not been replaced 3rd generation ones, I would have them replaced now.
Use these 2 websites links to views the information on tensioners problem:
http://www.jagservice.net/jaguar_v8_...tensioners.htm
http://www.jcna.com/library/tech/tech0028.html

Also do a forum search using "tensioners" limit it to the forums of Jaguar sections XJ8 & XJR; XK8 &XKR. That should give enough information on these tensioner problems (posts give others' experiences, DIY, Costs, etc).
Hope this helps.