It’s no great shakes. Mine was a simulated VFR flight, along the lines of:
Take off from A/G equipped airfield
Penetrate MATZ
Penetrate class ‘D’ airspace
Contact en-route frequency
Pass PAN call for a vessel in distress
Arrival at an ATC equipped airfield, with MAYDAY on downwind.
You’ll get a sheet with all the appropriate frequencies, and a chart with all the relevant information on. Within reason, you can take as much time as you like between calls – the only stipulation being that the test can’t last longer than it would if it was a real flight. You’ll certainly have enough time to write down each call before you make it, so no worries about getting tongue-tied.
As already said, if you have a decent working knowledge of CAP 413, you shouldn’t have any problems.