Hi Louise
     
     I have a suggestion for Buddy.
     
     I had a similar problem on my 87 westy.  My oil buzzer and light would 
     seemingly randomly go on and off much as you have described.  I 
     replaced both switches to no avail.
     
     Eventually I noticed that the buzzer wasn't particularly random.  It 
     would gradually get more and more frequent until I performed an oil 
     change.  After a change, it would go away for a while and then start 
     again.
     
     The problem I was having was the weight of oil I was using.  I was 
     running 10w30, which I believe is within the spec in Bently for 
     certain temperature ranges.  I changed to 20w50 and have not heard the 
     buzzer in 9 months.
     
     I think it is the list consesus to run 20w50, but I'm sure I'll be 
     corrected if this is wrong.
     
     Hope this helps.