If you still want to attend, but got an option for accomodation outside the Maritim hotel, then all you have to do is to write a mail to reg@eurofurence.org, and tell them. They will then take you off the waiting list, and you only have to pay for the convention ticket.
If you no longer want to attend Eurofurence at all, do the same: Send an email to reg@eurofurence.org and let them know that you no longer want to attend, and they'll let everyone else on the waiting list move on.