Further to GazDerby88's comments, I would add that when you set up the tournament, MAKE SURE the difficulty is county/test, and not slog.
Given for almost all of the game you will be used to leaving it on slog, and just adjusting overs,innings and realism, I completely forgot about this - until 2 hours later, when I won the tournament and it didn't unlock, and I finally worked out what I hadn't done.
Beware, county is a lot trickier than slog for batting (not so much bowling)- the ball does not always land where the cursor shows, and the timing is also harder. I went from hitting 20-30 runs an over on slog, to 5-10 an over in county. This makes keeping their score down key, and as such bowling just inside the crease, but well away from the batsmen is a better strategy here, than trying to get 10 wickets. Either way, this acheivement will take between 2-3 hours to get.