Looking at the prices, a plain trip won't get any cheaper then 80 euros. More likely it'll be closer to a hundred, and that's without a hotel. I did find a few train ferry combo tickets for around a hundred for two persons, but that's a return ticket to and from a Dutch train station.
The cheapest option seems to be a bus trip, eurolines. The promo youth ticket, which looks just as valid as a standard ticket, is 43 euros, round trip. The times are a horror, as far as I can see, so it'd either be a one-day affair, or I'd have to ask a classmate to keep my books and laptop over the weekend, and have my stuff with me at school on the monday. (That'd be fun to explain to my classmates...)
€43 sounds affordable, a hundred might become a small problem.
EDIT: I've found some 'reasonably affordable' lodging, 17,50 GBP a night, a place called the Generator. That would be 35 for a weekend, approx. 55 euros for two nights including breakfast. This is for a bed in an eight-bed dorm with shared bathroom. That would be way to expensive for me, but this seems to be one of the cheaper rates going. Lodging would be essential for me being able to go, but at least the travel seems affordable.