WordPress: Woocommerce – How do I display the proceed to checkout button only when the minimum amount is reached?

Solution:

According to what each of the values hold (from your comment), you could try one of the 3 scenarios below:

//min sale 250
if($postcode_present >= 250){
    $checkout_url = WC()->cart->get_checkout_url();
    echo '  <a href="'. $checkout_url .'" class="checkout-button button alt wc-forward">Proceed to Checkout</a> ';  
}
else 
{
    echo 'You must at least buy 250';  
}


//min sale 1 product
if( wc_cart_totals_order_total_html() >= 1 ){
    $checkout_url = WC()->cart->get_checkout_url();
    echo '  <a href="'. $checkout_url .'" class="checkout-button button alt wc-forward">Proceed to Checkout</a> ';  
}
else 
{
    echo 'You must at least buy 1';  
}

//min sale 1 product and 250 worth
if($postcode_present >= 250 && wc_cart_totals_order_total_html() >= 1)
{
    $checkout_url = WC()->cart->get_checkout_url();
    echo '  <a href="'. $checkout_url .'" class="checkout-button button alt wc-forward">Proceed to Checkout</a> ';  
}
else 
{
    echo 'You must at least buy 250 and min 1 product';  
}

also, using WooCommerce, you could enjoy some of the plugins that do this for you, like this or this.