validate-address1-not-uk-postcode.php

<?php
// Add to functions.php or using the Code Snippets plugin
// Do NOT include opening PHP tag above (<?php)
add_filter(
'woocommerce_default_address_fields',
		function( $fields ) {
			unset( $fields['postcode']['custom_attributes']['data-parsley-length'] );

			$fields['address_1']['custom_attributes']['data-parsley-pattern']       = '/^(?![A-Za-z][A-Ha-hJ-Yj-y]?[0-9][A-Za-z0-9]? ?[0-9][A-Za-z]{2}|[Gg][Ii][Rr] ?0[Aa]{2}).*$/';
			$fields['address_1']['custom_attributes']['data-parsley-error-message'] = __( 'Please enter a valid address.', 'your-translation-domain' );

			return $fields;
		},
		100001
);