NormalizePostcode.cs

public static string NormalizePostcode(string postcode) 
{  
//removes end and start spaces 
postcode = postcode.Trim();
 //removes in middle spaces 
postcode = postcode.Replace(" ", "");

switch (postcode.Length) {  
 //add space after 2 characters if length is 5 
 case 5: temp_postcode = temp_postcode.Insert(2, " "); break;
 //add space after 3 characters if length is 6 
 case 6: temp_postcode = temp_postcode.Insert(3, " "); break;
 //add space after 4 characters if length is 7 
 case 7: temp_postcode = temp_postcode.Insert(4, " "); break; 

 default: break;
 }
 return postcode; 
}

You could just do

temp_postcode = temp_postcode.Insert(postcode.Length - 3, " ");

wonder if this works internationally though?