How to Read Dataset row value from a Webservice

Hi...I need to consume a web service, which, when provided with State and Suburb, returns postcode.
The existing web service return DataSet, and produces the following XML.






















NORTH PARRAMATTA
1750
NSW



NORTH PARRAMATTA
2151
NSW



PARRAMATTA
1740
NSW






As it returns more than one row, I need to retirieve the Postcode value from the 1ST ROW only. I am using C# method to retrieve the Dataset value, but don't know how to do it.
My C# method in the code behind page to call the web service method is as below:
private DataSet GetPostcode(string txtSuburb, string txtState, string txtPostcode)
        {
                DataSet PostCodeSet = new DataSet();
                PostcodeService pcode = new PostcodeService();

                PostCodeSet = pcode.GetPostcodeAndSuburbForAustralia(txtSuburb, txtState, txtPostcode);     
            }
            return PostCodeSet;
        }

Here is what I have got in the Button_Click event of my Web Page:

DataSet PCodeSet = new DataSet();
PCodeSet = GetPostcode(StateList.SelectedValue.ToString(), HomeSuburbTextbox.Text.ToString(), null);
HomePostcodeLabel.Text = ??????????

So my question is how to populate the Label with the Postcode value from the 1st row. Any help would be really appreciated. Thanks.