Checkout confirmation page is not working with Mijireh

I'm using the MarketPress plugin, and we are using 'mijirah' for using worldpay. When we submit a payment, we get to this page
https://yoursite.com/checkout/confirm/?order_number=XXXXXXXXXX
which does not exist, but can't see where this is set.
Also - all of our links are root relative, which means they all break once using this.