One way of doing it is to just serve the .swf file directly, ie, if you go here
http://www.inkcreative.co.uk/Website.swf then the site displays exactly how you want it. So now all you have to do is make this page display when people enter your url. The best way of doing this is if you have php available create the following file called index.php
PHP Code:
<?php
header("Location: http://www.inkcreative.co.uk/Website.swf");
?>
(You will of course need to remove the old index.html file from the server otherwise this new php file will not display.)
Rob