In InitialiseField the question to load an existing file only accepts Y and not y

 1 static void InitialiseField(char[,] Field)
 2     {
 3       string Response = "";
 4       Console.Write("Do you want to load a file with seed positions? (Y/N): ");
 5       Response = Console.ReadLine();
 6       if (Response.ToLower() == "y")
 7       {
 8         ReadFile(Field);
 9       }
10       else
11       {
12         CreateNewField(Field);
13       }
14     }

Explanation

Line 6: Added .ToLower() in the if statement which means both 'Y' and 'y' will be treated as a lower case 'y'