Mark, you probably know, but check here for the ranked race timings.
http://game.raceroom.com/multiplayer-rating/The Rookie ones run all the time, the Pro & Am ones alternate every half hour, the Am ones require a 75 reputation, the Pro require 80. I don't think there is a minimum requirement for rating on those. You should be able to see all that are running even if you do not have the required reputation to join them.
There are also longer races which run at certain times in the evening & also the weekly enduro on a Wednesday evening.
You should able to see your rating & reputation in game if you go to the Portal then Ranked Multiplayer.
Just looked & there are currently 16 European Ranked servers running.