If you haven't done your Bronze theory exam there are several concepts in this course that may be new to you.
"Bronze and Beyond" is a very useful book which explains most of it, and is available from the BGA shop at a very reasonable £15.
Alternatively, Andrew Watson has published his Cambridge Gliding Club Bronze Air law lecture online. The slides are available at the link above, or a video of his talk is here .
You might particularly make sure you understand:
Flight level, Height, Altitude, transition altitude, transition level
ASR - Altimeter Setting Region
TAF, METAR, VOLMET, CAVOK,
VFR, VMC, IMC, IFR,
Degrees of the compass
What London Information/Scottish Information is
Controlled Airspace - MATZ, Zones, ATZ, RMZ, Parachute zones
The difference between heading and track
It would also be helpful if you were familiar with the the symbols on a standard half-mil map.