I'd agree with Jan - buy a cheap airband scanner and listen to the local traffic. R/T on the ground and in the circuit isn't particularly difficult so you should pick it up in no time and know when to say it.
Your instructor should ideally run through all the necessary R/T with you on the ground before you fly. Write the calls down and keep them on your kneeboard if you're not sure (I had to write down all possible calls when transiting Luton the first time I did it), it helps. Don't get flustered, relax and aviate first.
Remember, prefixing your call with "Student G-WXYZ" will generally make sure you don't get as much hassle if you get your calls wrong.