Thanks for you help Pete.

After some testing I found that the XSLT helper, JavaScript function and the C# functions all work on the basis of the current order or exisitng processed orders and I want to get the default delivery cost values before an order has been started.

The only solution I could find was to connect straight to the SQL database and extract the data that way.

Based on my installation only having one country and being interested only in the default standard shipping the following SQL command will get me the data I need (If you have multiple countries then you will need to update this based on the current country, likewise if you want to get all shipping options not just the first one)

SELECT     TeaCommerce_ShippingCurrency.Fee, TeaCommerce_ShippingCurrency.FreeShippingFromOrderTotalPrice
FROM         TeaCommerce_Country INNER JOIN
                      TeaCommerce_ShippingMethod_rel_Country ON 
                      TeaCommerce_Country.StandardShipmentMethodId = TeaCommerce_ShippingMethod_rel_Country.ShippingMethodId AND 
                      TeaCommerce_Country.Id = TeaCommerce_ShippingMethod_rel_Country.CountryId INNER JOIN
                      TeaCommerce_ShippingCurrency ON TeaCommerce_ShippingMethod_rel_Country.Id = TeaCommerce_ShippingCurrency.ShippingMethod_relCountryId
WHERE     (TeaCommerce_Country.IsDefault = 1)

Having checked / generated this in SQL Management Studio I then created some C# code to grab the data I wanted:

            String fee = "";
            String freeOver = "";
            String query = "SELECT TeaCommerce_ShippingCurrency.Fee, TeaCommerce_ShippingCurrency.FreeShippingFromOrderTotalPrice "
                + "FROM TeaCommerce_Country INNER JOIN TeaCommerce_ShippingMethod_rel_Country ON "
                + "TeaCommerce_Country.StandardShipmentMethodId = TeaCommerce_ShippingMethod_rel_Country.ShippingMethodId AND "
                + "TeaCommerce_Country.Id = TeaCommerce_ShippingMethod_rel_Country.CountryId INNER JOIN "
                + "TeaCommerce_ShippingCurrency ON TeaCommerce_ShippingMethod_rel_Country.Id = TeaCommerce_ShippingCurrency.ShippingMethod_relCountryId "
                + "WHERE (TeaCommerce_Country.IsDefault = 1)";
            SqlConnection connection;
            connection = new SqlConnection(GlobalSettings.DbDSN);
            connection.Open();
            using (SqlCommand command = new SqlCommand(query, connection))
            {
                SqlDataReader reader = command.ExecuteReader();
                if (reader.HasRows)
                {
                    reader.Read();
                    fee += reader["Fee"];
                    freeOver += reader["FreeShippingFromOrderTotalPrice"];
                }
            }

This code doesn't have any exception checking on the DB IO and outputs numerical data as string values (it was just some test code) but I thought I'd post this basic solution in case anyone else wanted to do something similar.

Anders / Rune, If I've missed the obvious and there is a better way of doing this please do tell me!