I need shipping costs to show in cart

I need to have shippingcosts showing in my cart. Normally the shippingcosts are added after the customer fills in his shippinginformation, or when a customer is logged in. I my case it means that customers don't see the final total amount until they are redirected to, in this case probably always, iDeal.

I only deliver in the Netherlands and only have 2 different shippingfees depending on the ordertotal.

1. Shipping = € 7,50 for order amounts of € 0,01 to € 149,00.

2. For orders with a total amount of € 150,00 and above shipping is free.

So I don't need to know the address before adding shipping.
I've been trying to find a solution here, but they don't exactly do what I want. For example:
https://premium.wpmudev.org/forums/topic/marketpress-solution-to-show-total-on-shipping-page-before-payment#post-214901

doesn't work for me because I have several payment gateways available (iDeal, PayPal and Manual Payment). This one works only for Paypal? (Please advise if I'm wrong about that).

The other possible solution I found came from @militarymama, it basically does what I want. But...
I've looked at her website and it seems to add extra costst whenever a single product is being ordered in higher quantities. (product x costst € 1.00 extra shipping is € 2,00, total € 3,00. When changing the quantity it also changes shipping which is not how it should be in my store.)

Any advise would be appreciated!

Regards,
Jolanda