Move captcha to just before the pay button on checkout page

At the moment the captcha box is tucked under the billing address and the border is around the state, phone email etc area.

I would like to move it to just before the payment button at the bottom of the page.

I have tried this:

remove_action( ‘woocommerce_after_checkout_billing_form’, array( $this, ‘c4wp_display_captcha’ ), 10, 0 );

add_action( ‘woocommerce_review_order_before_submit’, array( $this, ‘c4wp_display_captcha’ ), 10, 0 );

But it doesn’t work. PHP is not my strong point so I was wondering if there is something I am missing?

Thank you in advance for your help and for creating this great plugin!