Thanks for the reply.
The error message has gone, but on checkout if you try and remove a coupon, the screen does not show the coupon has been removed until the screen is refreshed. To me this looks like an AJAX issue. (Its works fine on the cart screen)
Also in System status it still shows
royal/woocommerce/cart/cart-totals.php version 2.1.0 is out of date. The core version is 2.3.6,
royal/woocommerce/cart/cart.php version 2.3.0 is out of date. The core version is 2.3.8,
royal/woocommerce/checkout/review-order.php version 2.1.8 is out of date. The core version is 2.3.0,