Reply Error Interception

Today's brainteaser:  I have a situation where the server returns a 403 error to users.

I wish to somehow intercept these and display a friendly "have a nice life" response instead of sending only the 403 header, which users' browser simply seem to swallow (I've only checked this on FF so far, which quietly disposes of the errors, giving the impression the site has become unresponsive (I suspect most of the other browsers would follow suit)).

It was seasonably easy to redirect 404's and 500's inside CI... and I already have an ErrorDocument 403 redirection in the .htaccess file that sends 403 errors generated by user's trying to get directory access to the 404 page (which seems to work nicely)… yet, when a 403 error is generated by CI giving a user the finger... the only way the user can tell is via the server's response header (and the unresponsive page), which the average user would not be any the wiser about.

I'd be grateful if someone could please point me in a sensible direction.

Thanks,
Gary