JJ,
For what its worth mate. I've begun taking
part in the hiring of people at Assessment Centres for a certain blue chip company.
For what its worth in the group ex. stuff -basically you need to demonstrate that you are a team player, who contributes positively to the tasks at hand. Sounds like basic stuff. However I would urge caution -you musn't put on an act. Rather, demonstrate how you would naturally
behave in a group situation. I certainly would be suspicious of anyone pretending to be 'all things to all men'.
Good luck!