MattD
In regards to what activities to do at Uni to help build your port folio for the RAF, simple answer: anything you enjoy.
The UAS will give you so much and you really have to make the most of the opportunities. The flying is fantastic, the adventurous training is amazing, the sport is brilliant and the guys/ gals you'll meet will be friends for life.
When I started Uni I also decided to take up some charity/ volunteering work, It has totally changed the way I look at life, some of the people I get to work with are tremendous individuals who have taught me some very valuable lessons. It takes up only 4 hours of my week and it really is worth looking into.
Best of Luck
Snoopy