Set MCPUK to relative path?

FOUND IT!!!!

In filemanager\browser\mcpuk\connectors\php\config.php

go to this line (line 42 for me):
$fckphp_config['urlprefix']=$fckphp_config['prot'].$_SERVER['SERVER_NAME'];

and replace it with:

$fckphp_config['urlprefix']="";


Hope this helps!