Add more space between form error message and input element
Adjust shipping address form input widths

To make it look a little more sensible.
Use larger order number to avoid clashes

When working in the sandbox, placing an order would fail as it would try
and use the same number as that of the fixture order. This change works
around that by using a higher order number for the fixture order.
Distinguish between 'preview' and 'confirmation' in checkout nav

This aligns the nav better with the checkout flow.
Add space after order contents within checkout displays
Improve checkout thank-you page

This change brings some of the labelling in sync with the preview page
and generally makes the page easier to understand.
Add padding to page bottom
Adjust widths of review form

They were too narrow beforehand.
Ensure user address form has same layout as shipping form
Fix bug with country field in shipping address form

Before this change, if you submitted a shipping address then navigated
back to the shipping address page, the selected country was lost. It's
possible this has been an issue for a while as the sandbox used to
default to only one shipping country which meant the country field was
removed.

The fix was to convert the country_id into a Country instance when
building the initial data for the form.