C# MVC UK Phone Numbers

How to format a telephone number as a UK standard format, according to https://en.wikipedia.org/wiki/National_conventions_for_writing_telephone_numbers with MVC HtmlHelper in C#

/// <summary>
/// Formats a UK phone number correctly
/// </summary>
/// <param name="htmlHelper" />
/// <param name="telephone" />The string version of the telephone number with no spaces.
/// <returns></returns>
public static MvcHtmlString PhoneNumber(this HtmlHelper htmlHelper, string telephone)
{
    Match match;
    if (telephone != null)
    {
        if (telephone.StartsWith("02"))
        {
         match = Regex.Match(telephone, @"(\d{3})(\d{4})(\d+)");
        }
        else if (telephone.StartsWith("011") || Regex.IsMatch(telephone, @"^01\d1\d+")) //starts 011 or 01x1
        {
         match = Regex.Match(telephone, @"(\d{4})(\d{3})(\d+)");
        }
        else if (telephone.StartsWith("01") || telephone.StartsWith("07"))
        {
         match = Regex.Match(telephone, @"(\d{5})(\d+)");
        }
        else if (telephone.Length == 11)
        {
         match = Regex.Match(telephone, @"(\d{4})(\d{3})(\d+)");
        }
        else if (telephone.Length == 10)
        {
         match = Regex.Match(telephone, @"(\d{4})(\d+)");
        }
        else
        {
         match = Regex.Match(telephone, @"(\d{5})(\d+)");
        }
        
        if (Regex.IsMatch(telephone, @"^01\d1\d+"))
        {
         return MvcHtmlString.Create($"{match.Groups[1]}-{match.Groups[2]} {match.Groups[3]}");
        }
        
        List numberChunks = new List();
        
        if (match.Success)
        {
         for (int i = 1; i < match.Groups.Count; i++)
         {
          numberChunks.Add(match.Groups[i].Value);
         }
        }
        
        return MvcHtmlString.Create($"{string.Join(" ", numberChunks)}");
    }
    return null;
}