Which Scolarship is it at age 23? It depends on the scholarship if it is the full battery of tests - for instance the Flying Scholarship tests are not the full ones - gives you a reasonable idea of how you will perform in the full ones though.
The computer (hand-eye etc) test are alot more indepth than any airline selection I'v been on - but who did you do yours with?
If you are going for 'cadet' i assume you mean you are at univeristy? In which case I don't think the 23 upper age limit applies - although that info will be clear in the reams of paperwork they give you beforehand.
Definately enquire about a career - you are there to show interest and put yourself ahead for a career with them - not just to get something for free!
All current affairs - obviously pay a little more attention to those defence related - as in MOD cutbacks - how will that affect the RAF's affectiveness? Also those international current affairs that have, or are likely to involve UK military intervension. Think back aswell - know about recent conflicts - back to Bosnia etc.
So concentrate on those events which affect the RAF but also spend time on other things -such as fuel prices (why are they so high...middle east tensions) to show a depth and breadth of knowledge and understanding.
Also - show you are cultured. That was my big black mark - everthing else was good except I was too narrow in my cultural interests - theatre etc.
As for group exercises, they are all well explained. Follow commands whilst part of the team, and put suggestions in a non-threatening helpful kind of way - do not undermime your 'commander'. There is little you can do for these other than to know the role your are expected to play in a given exercise - lead from the front but not authortarian. And know when to shut up when not leading!!
Hope that helps, post again if need more!
JP