Very many thanks to @zerogjoe​  for his elegant answer, which works perfectly for Databricks formatted file paths.

To make this a little more robust and allow for filesystem api paths (that can be used with os, glob etc and start with "/dbfs") I've added a few lines of code.

def exists(path): """ Check for existence of path within Databricks file system. """

if path[:5] == "/dbfs":
     import os
     return os.path.exists(path)
 else:
     try:
         dbutils.fs.ls(path)
         return True
     except Exception as e:
         if 'java.io.FileNotFoundException' in str(e):
             return False
         else:
             raise