Slightly off topic but lots of English managers may see this thread so I thought I should say that training for the u21 has made the game so much more enjoyable for me whilst in d3.
Any new/d3 managers who maybe aren't sure about the game yet, thinking of quitting or just getting bored of arena building and playing bots, should definitely consider getting involved in the NT teams, especially through training. It really does make the long, hard slog up the divisions worth it.