The effect of prop rotation direction is modeled in AH. But it's not that all British fighters use counterclockwise rotation - only Typhoon and Tempest (and the Yak's) do.
You can see it when starting up the engine, and you can feel it when taking off without autotakeoff.
It doesn't really create an advantage as such. It basically just means your plane will roll quicker (and turn somewhat better) to the right at full power. You may be able to use that to your advantage, but so may your enemies use their quicker roll to the left.