Woocommerce remove VAT for non GB / UK

abt-modify-prices.php

<?php
/*
Plugin Name: Abikething modify pricing display
Plugin URI:  http://pauldrage.co.uk
Description: This plugin over rides the pricing display to handle GB versus ROW for tax. Requires plugin woocommerce_set_country to set $_SESSION wc_country_iso
Version:     1.0.0
Author:      Paul Drage
Author URI:  http://pauldrage.co.uk
License:     GPL2 etc
License URI: https://
 */

// Simple, grouped and external products
add_filter( 'woocommerce_product_get_price', 'single_price_without_tax', 10, 2 );
add_filter( 'woocommerce_product_get_regular_price', 'single_price_without_tax', 10, 2 );

// Variations 
add_filter( 'woocommerce_product_variation_get_regular_price', 'var_price_without_tax' , 99, 2 );
add_filter( 'woocommerce_product_variation_get_price', 'var_price_without_tax', 99, 2 );
add_filter( 'woocommerce_show_variation_price', 'var_price_without_tax', 10, 3 );

// Variable (price range)
add_filter('woocommerce_variation_prices_price', 'var_price_without_tax', 99, 3 );
add_filter('woocommerce_variation_prices_regular_price', 'var_price_without_tax', 99, 3 );

// Handling price caching (see explanations at the end)
add_filter( 'woocommerce_get_variation_prices_hash', 'add_price_multiplier_to_variation_prices_hash', 99, 1 );


function var_price_without_tax( $price, $variation ) {
    
    if (!session_id()) {
		session_start();
	}

    if (isset($_SESSION['wc_country_iso'])) {
        if (strlen($_SESSION['wc_country_iso']) == 2) {
            if ($_SESSION['wc_country_iso'] == 'GB') {

                return round($price,2);
                
            }
        }
    }

    $price_excluding_tax = round(($price / 120) * 100,2);
    return round($price_excluding_tax,2);

}

function single_price_without_tax( $price, $product=false ){

    if (!session_id()) {
		session_start();
	}

    if ($price) {
        if (isset($_SESSION['wc_country_iso'])) {
            if (strlen($_SESSION['wc_country_iso']) == 2) {
                if ($_SESSION['wc_country_iso'] != 'GB') {
                    return round(($price / 120) * 100,2);
                }
            }
        }
    }
    
    return $price;
}

function add_price_multiplier_to_variation_prices_hash($hash) {

    // woocommerce cache for variation prices:
    // https://developer.woocommerce.com/2015/09/14/caching-and-dynamic-pricing-upcoming-changes-to-the-get_variation_prices-method/


    // whilst developing:
    // WC_Cache_Helper::get_transient_version( 'product', true );

    if (!session_id())
    {
		session_start();
        if (isset($_SESSION['wc_country_iso'])) {
            if (strlen($_SESSION['wc_country_iso']) == 2) {
                $hash[] = $_SESSION['wc_country_iso'].'_'.get_current_user_id();

                // early return
                return $hash;
            }
        }
	}

    $hash[] = get_current_user_id();
    return $hash;

}