It's a good idea to do some prep for any test or exam but 2 hours sounds a bit OTT.
The test itself is very straightforward:
W&B and perf calcs
NOTAM and wx brief
usual checks, etc
Climb at Vx and Vy
A couple of stall recoveries
Steep turns
PFL
A little Nav
EFATO
Circuits
Details are in the examiner's check list:
http://www.caa.co.uk/docs/33/FORSRG1157.pdf
http://www.advisorybodies.doh.gov.uk...119tox0710.pdf
HFD