There isn’t any really. It’s fairly complicated. (I don’t think XPlane 12 will be significantly better ATC, though probably better than 11s which is bad).
Why don’t you want to use VATSIM ?
The main problem people have with VATSIM is nerves I think, worrying about making an idiot of themselves. VATSIM (and IVAO, used more if you are mainland Europe) quite often run beginners events where they handhold people through their first flight.
And the ATC are quite helpful. If you turn up at EGLL in the rush hour they won’t have the time, but if you start at a quieter airport with not much happening and signify yourself as a beginner most will try to help you. If you look on Vattastic or Webeye (?) they will tell you what places have ATC and how busy they are.
And nobody really minds mistakes as long as you don’t spoil it for other people. Avoid the #1 no-no - connecting on the runway so you just appear there to the controller.