Then we need to inform our customer with messages

/**
 * @snippet       WooCommerce: Define Minimum Order Amount & Show Errors
 * @sourcecode    https://businessbloomer.com/?p=19947
 * @author        Rodolfo Melogli + Marc Bovet
 * @testedwith    WooCommerce 2.5.2
 * @date		  14.11.2016
 */
 
add_action( 'woocommerce_checkout_process', 'gastronomy_wc_minimum_order_amount' );
add_action( 'woocommerce_before_cart' , 'gastronomy_wc_minimum_order_amount' );
 function gastronomy_wc_minimum_order_amount() {
	
	//if cart is empty, there is nothing to display.
	if ( WC()->cart->get_cart_contents_count() == 0 ) {
			return;
	}	
	
	//TODO:
	//minimum order amount is not required for local pickup
	//return from here.
	
	// CAUTION
	// !!An order can only have products from 1 and only 1 vendor !!
	// get first product of the cart => then we can get vendor ID	
	$items = WC()->cart->get_cart();
	foreach($items as $item => $values) {
		$_product[] = $values['data']->post;
	}	
	
	$vendor_id = get_post_field( 'post_author', $_product[0]->ID);
	
	//get minimum order amount
	$minimum = get_user_meta( $vendor_id, 'wcv_custom_settings_minimum_order_amount', true ); ;
	
	//Minimum order amount
    //Inform user that a minimum order amount is required.
    if ( WC()->cart->subtotal < $minimum ) {
			$text = sprintf( __('You must have a minimum order amount of %s to place your order. Your current order total is %s.') , 
                    wc_price( $minimum ), 
                    wc_price( WC()->cart->subtotal )
            );
	
        if( is_cart() ) {
            wc_print_notice($text,'error');
 
        } else {
 
            wc_add_notice( $text,'error');
 
        }
		return; //comment to display remaining amount to get free shipping.
    }
	//End minimum amount.

	
	//Show remaining amount to reach free shipping
	$minimum_amount_free_shipping = get_user_meta( $vendor_id, 'wcv_custom_settings_free_shipping_amount', true ); ;
	$delta = $minimum_amount_free_shipping -  WC()->cart->subtotal;
    if ( $delta>0) {
		
		
		$text =  sprintf( __('You only need to spend %s to get FREE shipping !') ,wc_price($delta) );
				
        if( is_cart() ) {
			
            wc_print_notice($text,'notice');
			
         } else {
 
            wc_add_notice($text,'notice');
 
        }
    }
	//End amount free shipping	
	
 
}

When free shipping is available, hide other methods.

/**
 * @snippet       WooCommerce : hide all shipping methods when free is available.
 * @sourcecode   https://gist.github.com/mikejolley/11171530
 * @testedwith    WooCommerce 2.6.8
 * @date		  15.11.2016
 */
add_filter( 'woocommerce_package_rates', 'adjust_shipping_rates', 10, 2 );
 
/**
 * Hide shipping rates when free shipping is available
 *
 * @param array $rates Array of rates found for the package
 * @param array $package The package array/object being shipped
 * @return array of modified rates
 */
function adjust_shipping_rates( $rates, $package ) {
 	
 	// Only hide rates if free_shipping is present
  	if ( isset( $rates['free_shipping:9'] ) ) { //use firebug to get the exact name for free shipping.
  	
  		// To unset a single rate/method, do the following. This example unsets flat_rate shipping
  		unset( $rates['local_pickup:5'] );
		unset( $rates['wcv_pro_vendor_shipping'] );
  		
	}
	else //adjust vendor shipping cost with required value.
	{
		// CAUTION
		// !!An order can only have products from 1 and only 1 vendor !!
		// get first product of the cart => then we can get vendor ID	
		$items = WC()->cart->get_cart();
		foreach($items as $item => $values) {
			$_product[] = $values['data']->post;
		}	
	
		$vendor_id = get_post_field( 'post_author', $_product[0]->ID);
	
		//get shipping fees from vendor.
		$fee = get_user_meta( $vendor_id, 'wcv_custom_settings_shipping_fees', true ); ;
		
		//update shipping fees with vendor shipping fees.
		if(isset($rates['wcv_pro_vendor_shipping'])){
			$rates['wcv_pro_vendor_shipping']->cost = $fee;
		}

	}
		

	return $rates;
}

@fervous
you’re welcome.
I forgot to mention that WC Vendors needs to be configured like this in the backend :
1° WC vendor shipping needs to be activated
2° Shipping System : Flate Rate
3° Procut Cost Nationally set to a value > 0

read carefully the comment in the provided code.

cheers,

@digitalchild

yes I prevent customers that they can only order products from 1 vendor (code is not provided), it can be done in the functions.php file.
A customer can have more than 1 product in the cart.
As there is no realease date for the 1.4 I have to find solution to progress….

@fervous
yes I’ve plannned to use ghist but no time for that right now.
I did not modified WC vendors but only used functions in my functions.php file.

cheers,