Sadly I've had to completely rule out travel on the 23rd. Exams finish way too late to get from the exam building to the station to the airport, even if I have my bags with me in the exam.

AMS is more expensive than going through BRU, and the Dutch railways are as notorious as LHR for shutting down in the bad weather. Zaventum, even if the railways are on go slow because of the weather, is much closer and therefore cheaper in a taxi in event of IRROPS. And sleasyjet charge the same for baggage. Plus, the train to and from AMS can add anywhere between €24 and €50.