RT Practical.
I assume they're all the same. I did mine at Wolverhampton.
The examiner will give you a ficticious aviation map with a route on it for you to pretend to fly. You sit in one room with headset, PTT and a box with a frequency selector switch. Basically, you do the whole route from engine start and taxi, through MATZ and airspace penetrations, Danger area crossings and landings away etc, with your examiner being in an adjacent room being the controller at each location. If you forget to, or change to the wrong channel, of course, he will not answer you etc.
You get preparation time before the practical test - ie examiner gives you the map and your route instruction sheet and a pencil and paper for you to make notes. Don't try to write ALL your calls down, just prompts is best. Half an hour I think the prep time is.
Anyway, I found it hugely enjoyable. And the examiner is not really out to trip you up or fail you, just to help you get your certificate. If it is available to you, pay for a couple of hours practical instruction before hand. It gets you right in the mood.
Good luck with it.