This will redirect
domain.com
www.domain.com
domain.co.uk
www.domain.co.uk
www.domain.net
to domain.net
RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_HOST} !^excludedsubdmain.(.*)$ [NC]
RewriteCond %{HTTP_HOST} ^((www.)?domain.(com|co.uk)|www.domain.net) [NC]
RewriteRule ^(.*)$ http://domain.net/$1 [L,R=301]