How do I have download button point to mirrored site

My website has a mirror of the download directory in the U.K.. On my download page I have 2 buttons, one for a U.S. download and one for a U.K. download. The current download page passes the filename to the download script. The download script (located in the download directory) for the U.S. download reads as follows:

<?php

$php_scripts = '../../php/';
require $php_scripts . 'PDO_Connection_Select.php';
require $php_scripts . 'GetUserIpAddr.php';
function mydloader($l_filename=NULL)

{
$ip = GetUserIpAddr();
if (!$pdo = PDOConnect("foxclone_data"))
{   
    exit;
}
    if( isset( $l_filename ) ) {  
        header('Content-Type: octet-stream');
        header("Content-Disposition: attachment; filename={$l_filename}");
        header('Pragma: no-cache');
        header('Expires: 0');        
        readfile($l_filename);

        $ext = pathinfo($l_filename, PATHINFO_EXTENSION);
        $stmt = $pdo->prepare("INSERT INTO download (address, filename,ip_address) VALUES (?, ?, inet_aton('$ip'))");
        $stmt->execute([$ip, $ext]) ; 

        $test = $pdo->query("SELECT lookup.id FROM lookup WHERE inet_aton('$ip') >= lookup.ipstart AND inet_aton('$ip') <= lookup.ipend");
        $ref = $test->fetchColumn();
        $ref = intval($ref);

        $stmt = $pdo->prepare("UPDATE download SET lookup_id = '$ref' WHERE address = '$ip'");
        $stmt->execute() ;         
      }

    else {
        echo "isset failed";
        }  
}
mydloader($_GET["f"]);
exit;

How do I modify it to download from the mirrored download directory if they select the U.K. download button. I think the download page will need to point to a separate download script for the U.K. download, but I'm not sure how to code it.