Default Shipping cost

Hi,

Does anyone know what sets the default shipping cost?

I have four shipping methods, one £100, one £50 and two that are free.

When I have an item in the basket though it defaults to the £100 cost until a different method is selected. Is there any way to change the default method selected? Or even better have no shipping selected until the customer has manually selected it from the perch_shop_shipping_method_form()?

Thanks!