shipping costs calculation

Hi there,

We would like to add in our shipping costs a rule for customers that want to buy 2 or more products.

We have like this prices for the shippinh costs:

Ireland 6€ for 1 product, We would like to have 5€ shipping costs for 2 or more products each one. And the other zones the same:

Uk 10€ for 1 product, to 8 for 2 or more products each one.
Europe 12€ for 1 product, to 10 for 2 or more products each one.
World 15€ for 1 product, to 12 for 2 or more products each one.

So to do that which way should be the best?

Thank you.