How to change / for x month text on a WooCommerce variable subscription product

Similar to This but not entirely.

I have a variable subscription product that can be paid over 12 monthly instalments.

if "Number of Instalments" is "Pay in Full" Id like to be able to change the £xxx for 1 month text:

And then keep the next 11 installments as for 2 month / 3 month etc.

I know that this code will only show the prices but I cant seem to modify it to only alter the 1 month (Pay in Full option):

add_filter('woocommerce_subscriptions_product_price_string_inclusions', 'remove_subscription_inclusions', 10, 2);

function remove_subscription_inclusions( $include, $product ) {
    $include['subscription_length'] = '';
    $include['subscription_period'] = '';
    return $include;
}

I did try this but it did not have any effect:

add_filter('woocommerce_subscriptions_product_price_string_inclusions', 'custom_subscription_price_string_inclusions', 10, 2);

function custom_subscription_price_string_inclusions( $include, $product ) {
    // Check if the product is a subscription product
    if ($product->is_type('subscription')) {
        // Get the variations of the subscription product
        $variations = $product->get_available_variations();

        // Loop through each variation to check for the 1-month payment option
        foreach ($variations as $variation) {
            // Get the variation's price and subscription length/period
            $regular_price = $variation['display_price'];
            $subscription_length = isset($variation['attributes']['pa_subscription_length']) ? $variation['attributes']['pa_subscription_length'] : '';
            $subscription_period = isset($variation['attributes']['pa_subscription_period']) ? $variation['attributes']['pa_subscription_period'] : '';

            // Check if this variation is the 1 month (single payment) option
            if ('1' === $subscription_length && 'month' === $subscription_period) {
                // Modify the price string for the 1 month single payment option
                $include['price_string'] = '£' . $regular_price . ' (Full payment for 1 month)';
                // Remove subscription length and period to avoid duplication
                $include['subscription_length'] = '';
                $include['subscription_period'] = '';
            }
        }
    }

    return $include;
}

This is how I got it working: I used javascript/jQuery as it works regardless of WooCommerce internal class differences.

add_action('wp_footer', 'custom_replace_subscription_price_label');

function custom_replace_subscription_price_label() {
    // Only run this script on single product pages
    if (!is_product()) return;

    // Output JavaScript to modify price display dynamically
    ?>
    <script type="text/javascript">
        jQuery(document).ready(function($) {
            // Hook into variation change event on product page
            $('form.variations_form').on('show_variation', function(event, variation) {
                
                // Find the price container
                var $priceEl = $('.woocommerce-variation-price .price');

                // If variation or price data is missing, stop here
                if (!variation || !variation.price_html) return;

                // Grab the HTML of the price string
                const rawHTML = variation.price_html;

                // If the price string contains "for 1 month", replace it
                if (rawHTML.includes('for 1 month')) {
                    const updatedHTML = rawHTML.replace(/for 1 month/, 'Pay in Full');
                    
                    // Update the HTML in the DOM with the new version
                    $priceEl.html(updatedHTML);
                }
            });
        });
    </script>
    <?php
}

//FOR CART & CHECKOUT

// Modify the price column in the cart
add_filter('woocommerce_cart_item_price', 'custom_replace_subscription_price_cart', 10, 3);

// Modify the subtotal column in the cart
add_filter('woocommerce_cart_item_subtotal', 'custom_replace_subscription_price_cart', 10, 3);

function custom_replace_subscription_price_cart($price_html, $cart_item, $cart_item_key) {
    // Check if the price string contains "for 1 month"
    if (strpos($price_html, 'for 1 month') !== false) {
        // Replace it with "Pay in Full"
        $price_html = str_replace('for 1 month', 'Pay in Full', $price_html);
    }

    // Return the modified (or unmodified) price string
    return $price_html;
}