Redirect code works 1st time then not subsequent times???

Hi,
(Dreamweaver CS4, Firefox on PC)
website is www.crookseys.co.uk
I set up website with homepage of index.html.
Visitors click 'enter site' & go to home.php
I've added password_protect.php to home.php & modified to redirect visitors depending on username:
i.e.

Code:

$LOGIN_INFORMATION = array(
'lunch' => 'monkey',
'bbq' => 'chimp'
);

// attempt to redirect user logins
$REDIRECTS = array (
'lunch' => 'monkey.php',
'bbq' => 'chimp.php'
);

Then just before ?> I've added :

Code:

header('Location: '.$REDIRECTS[$login]);

PROBLEM IS:
Code works well first time& redirects correctly. But, if I retype web address in address bar to get back to index.html, then click 'enter site' again, the index.html just reloads instead of going to home.php
N.B. didn't have this problem before modifying the code to redirect.
Would love help a.s.a.p
Thanks for this code so far - love it