[Holub]

I've wrote "You should know paymentid of the selected payment method (if you have more than one payment method)."
Paymentid must be equal of selected by customer. Otherwise this will not work.
I've tested this at your site and I'm sure that this method working properly.
I've registered in your shop as Holub_from_forum. At 'Select payment method'checkout step I've selected 'Money Order' (from HTML source - paymentid=7). At last step I've returned to home.php and try to use url `http://easycoffee.com.au/cart.php?mode=checkout&paymentid=7` - and I was redirected to last checkout step 'Place order'.
Therefore, your shop should to `remember` selected paymentid and redirects customer to cart.php?mode=checkout&paymentid=(selected_payment _method_id)