It sounds hard but it really isn't as bad in practise if
you've done any radio work and take a good look at
your CAP413 booklet.
You are given a radio set with a variety of preset
frequencies and a map with a planned route.
The examiner will run through a practise session with you
first of all, ironing out any issues with terminology
that you have. Take this practise!
Then you get to do a live flight with a variety of potentially
exciting things going on...expect Mayday's, rerouted MayDays,
Pan's...diversions etc but just play it by the book.
Keep cool, listen carefully and don't sweat it too much, in my
experience it is a very fair exam,
-- Andrew