All the Trevor Thom books are good, but make sure they are the new JAA ones.
When I was practicing for my RT Exam, I was told to plan imaginary routes all over the country and aswell as doing the Nav. preparation (good for helping with the Nav exam too) , go through what you would need to say over the radio, and who you would need to talk to, from start up to touchdown. At first write everything down, including what may get said to you from ATC etc. then do just your bits ad lib for a a few routes.
The RT practical is a made up route, which is done in exactly this way, they let you make notes to plan who you need to talk with too.
This excercise is just an extension of your normal pre-flight planning for a X-country, I found it good fun.
Be sure to bone up on MATZ/CTR crossing, Special VFR and diversions/being lost, and you will definitely need to know Mayday/Pan calls.
Good luck, SD.