Call again...

and check the Virgin Express and SN Brussels websites. They certainly don't seem to have merged yet, though it is in the works. (Hint: Google works pretty well as a search engine.)

I believe you can interline bags with SN, but TV I am not sure of - many LCCs do not have interline agreements with major airlines. I'd fly checked baggage free on this one.

As far as five hours - not that much to do at Zaventem, but I suppose you ould take the train to Gare Centrale and head to Rue des Bouchers for lunch.

I see TV offers more legroom up front and first service, as well as seat selection, for pay! Hmmm, I can see wheels and cogs turning...

"For just €10 each way, you can enjoy an extra 7.5cm (about 3") extra legroom, for even more comfort on board.
All the space you need to arrive refreshed.
Located between rows 2-7, so the onboard service reaches you first.
Be the first off the plane." and

"Make your flight more enjoyable and pre-book your preferred seat for only €2,5 extra (one way)!" (e.g. if you want to assure you sit with someone else, that's five quid.)