I rang the Maldron again yesterday. They said that there was a link you could click on when buying tickets. A few managed to book this way before the big convention was confirmed. She said they definitely have not booked any speedway fans in directly through the hotel.
She also mentioned that the convention was known about when they agreed the speedway date and that a lot of the hotels would be booked up leaving a lot of people going to speedway with nowhere to stay.
I guess we'll be trying further afield as you suggest A Orlov.