Thanks for the reply Ray - I really appreciate you taking the time.
You believe that they have set the path incorrectly in the options panel or that the driectory itself containing these elements is not created?
I have uploaded the test file to another website I have hosted - this is php 7.3 (the other site being php 5.6) and the error is different:
http://hollandcreative.co.uk/sessionTest.php
I've looked into the php options set up in my cPanel and it is as follows (for php 5.6)
include_path - .:/opt/alt/php56/usr/share/pear:/opt/alt/php56/usr/share/php
session.save_path - /opt/alt/php56/var/lib/php/session
I know all hosting companies have different directories, but does that look OK to you?