I've got two countries set up:

    United Kingdom
    Australia

and I've also set up different VAT rules for each one where the UK pays VAT and Oz does not.

I've also got two payment methods set up:

    Account
    PayPal Sandbox

There isn't a step that allows the selection of the payment method in my cart as in reality there will be only one in use for now, but for testing purposes:

The 'Standard payment method' for the UK is set to Account (as per the starter kit).
The 'Standard payment method' for Australia is set to PayPal Sandbox.

So I'm expecting these defaults to be used.

On my customer information page I ask the user to select their country and I then set the current country accordingly using the following .Net code.

protected void saveLinkButton_Click(object sender, EventArgs e)
        {     
                if (Page.IsValid)
                {
                    TeaCommerce.Base.UpdateOrderProperty("company", companyTextBox.Text);
                    TeaCommerce.Base.UpdateOrderProperty("firstName", firstNameTextBox.Text);
                    TeaCommerce.Base.UpdateOrderProperty("lastName", lastNameTextBox.Text);
                    TeaCommerce.Base.UpdateOrderProperty("email", emailTextBox.Text);
                    TeaCommerce.Base.UpdateOrderProperty("telephone", telephoneTextBox.Text);
                    TeaCommerce.Base.UpdateOrderProperty("streetAddress", addressStreetTextBox.Text);
                    TeaCommerce.Base.UpdateOrderProperty("zipCode", addressPostcodeTextBox.Text);
                    TeaCommerce.Base.UpdateOrderProperty("city", addressCityTextBox.Text);
                    TeaCommerce.Base.UpdateOrderProperty("country", addressCountryDropDownList.SelectedItem.Text);
                    TeaCommerce.Base.UpdateOrderProperty("countryID", addressCountryDropDownList.SelectedValue);
                    Country selectedCountry = TeaCommerce.Data.Country.GetCountry(long.Parse(addressCountryDropDownList.SelectedValue));
                    TeaCommerce.Base.UpdateOrderProperty("ISOCountryCode", selectedCountry.CountryCode);
                    TeaCommerce.Base.UpdateOrderProperty("comments", commentsTextBox.Text);

                    TeaCommerce.Base.SetCurrentCountry(selectedCountry.Id);

                    Response.Redirect(new Node(_continuePageID).Url);

                }              
        }

If I select Australia as the country, no VAT is added as expected and when calling

TeaCommerce.goToPayment();

I'm sent to the Sandox OK.

If I then exit out of the Sandbox, and go back to the customer information page and select the UK as the country, the VAT gets added as expected but I'm still being re-directed to the PayPal Sandbox.

It's doesn't seem to be taking into account the payment method for the country.