Hi Dave,
for details of how to update only part of Moodle from CVS see:
http://moodle.org/mod/forum/discuss.php?d=24922
This would seem to suggest the following command would update the hotpot module:
cvs update mod/hotpot
Now you just need to work out how to run that command regularly using cron. Probably a Google serach for "cron" or "cron guide" will lead you somewhere useful. The following link looks promising:
http://www.unixgeeks.org/security/newbie/unix/cron-1.html
When you have nailed down something that works, please consider posting your solution here or on the MoodleDocs site
all the best
Gordon
