I want to use the zones shipping module but it does not seem to have the flexibility I need.

I want to charge the following shipping rates:

UK and Western Europe
$15-00 for the first item plus $10.00 for each additional item

South Africa
$15-00 for the first item plus $5.00 for each additional item

Asia
$15-00 for the first item plus $10.00 for each additional item

How could this be achieved please?