Additional charges in ecart object

1. Currently on the client's site only UK customers purchase in sterling using worldpay and the admin and carriage charges are as follows in the ecart object:

Admin charge - flat rate of £10 for all orders under £200 - above this no charge
Carriage charge - flat rate of £15 for all orders under £400 - above this no charge

If a US or Canadian customer logged in, how can additional chages for admin and carriage be applied based on their country of origin?

2. What is the correct way to add United States and Canada to the "is equal to" operator along with United kingdom in the if statement below

<?php if(isset($_SESSION['UserCountry']) && $_SESSION['UserCountry'] == "United Kingdom") { ?>

1) Create additional shipping chargers using the Session Variable equal to trigger and use the UserCountry session variable

2) to Us an canada to the if statement, add an or condition:

<?php if(isset($_SESSION['UserCountry']) && ($_SESSION['UserCountry'] == "United Kingdom" || $_SESSION['UserCountry'] == "United States" || $_SESSION['UserCountry'] == "Canada")) { ?>