Other good spotting sites in BRU:
When you are in the departure hall (landside), take the elevator up to the highest level. The "Promenade" level. Than go to the self-service restaurant in the back. Choose your spot and you can overlook the runway, the new B-pier, the new A-pier in construction or the cargo (DHL) site. This place is also accesible for non-travelers.
When you are in the tax free area in the new building, go to the top level and there you will find a self-service restaurant with a view on the B-pier and on the runway. Go to the other side of the top level (to the bar) and there you will have a view over the runway and the place where the planes are parked at an "external" position.
In the C-terminal you can spot the planes from the waiting area after you went down the stairs at the security control (this is for departing pax). When you arrive, you can go to the same spot, it is situated at the doors to go to the luggage hall.
But the best viewings yu can find in the Sabena restaurant. It is in the old airport builiding on level 8. From that point you can overlook the entire airport.
Now about Virgin Express. Like said before, it is a low-cost carrier. Don't expect the "grand luxe". It's actually a funny airline because there is totaly no organisation. It's a balst to see the employees struggeling with there papers trying to find some structure in their mess.