Interestingly from the VEX website and the departure info at Brussels airport, it appears that VEX and DAT/Sabena are no longer codesharing, with DAT keeping the original slots and VEX having to fit in where there is room and cut the number of flights.
I guess this answers the original question, but I can't imaging VEX are happy. Is this really happening? Are there now 4 carriers flying LHR-BRU?! Are there this many passengers?
G-Inger