[B00MER]

	# force to payment page if only one payment method is available	
	if(!$payment_methods[1]){	
		func_header_location("cart.php?mode=checkout&paymentid=".$payment_methods[0][paymentid]);	
	}

Add the above to customer/cart.php after the following code:

#
# Show checkout page with payment options only methods availiable to current 
#  membership level are displayed
#
	$membership = $user_account["membership"];
	$payment_methods=func_query("select * from $sql_tbl[payment_methods] where active='Y' AND (membership='' OR  membership='$membership') order by orderby");

\