Add fields to Checkout -> Billing Details

Hi,

Currently at my webshop when people check out and fill in their billing details they are asked to fill in:

-First name
-Last name
-Company name
-Country
-Street address
-District
-Province
-Phone
-Email address

I would like to make a couple of adjustments there so that it becomes:

-First name
-Last name
-Company name
-City
-District
-Ward
-Street name
-House number
-Phone
-Email address

None of these need to be drop down menus by the way.

The page I need help with: [log in to see the link]