Hi Paul,
Don't be nervous at all. The examiner just wants to see that:
a) you can plan - plog, weight + balance etc
b) you can navigate - timekeeping, airmanship, following headings etc
c) you can communicate - radio work
d) you won't get him/her lost
e) you can divert
f) you know your emergency procedures - stalls, spins etc
g) you know how to land the aircraft in different configurations
I think it's this document outlines what the examiner will want to see:
http://www.caa.co.uk/docs/33/Standar...19_A%20v6_.pdf
although your flying school will probably have its' own version.
Most of all be relaxed. Think of it as another long flight, not a test. You basically need to prove to your instructor that you won't get them lost, and the familiar phrase regarding would you be trusted to fly their children will get trotted out as well.
I was so nervous when I did my test I was sick. After landing I thought, "what the hell was I so worried about?". The examiner ended up being brilliant.
Watch out for any tricks, like the examiner pulling out the breaker for the stall warner when bringing the aircraft into a stall. Look out often. Check your timings. Always tell the instructor what you intend to do or why you did it, just in case they think you've forgotten to check this instrument or that altitude.
If you come across a difficult controller (like I kind-of did over the Benson MATZ), then stay calm. Remember your calls and the order in which you give your information. You've done your FRTOL so this should be good.
As you've done your PPL training intensively all this should still be fresh in the mind. Relax and treat it as a nice jaunt around the sky, you only need to show the examiner your skills. He or she will explain to you how the whole test will be conducted and put your mind at ease beforehand, they've seen thousands of worried students before.
Good luck!