[support] customising user search in admin

I'm having trouble customising the user search and help functions.

I have functions named theme_user_search and theme_user_help in my templates.php, but they appear not be getting used... all other theme_* functions are being used though.

Is there anything else I need to do? The core fuctions are in the user module - user_search and user_help. It mentions they are implemenatations hook_search and hook_help - do I need to customise these, too?

I have noticed pages are often cached - I have cleared out the cache tables in the DB, but that doesn't help.. so it appears my functions aren't being called.

I'm using Drupal 5.3 and PHP 5.2.4

Robert