Best thing to do is to keep checking at least once a day. They seem to release some new accommodation options on most weekdays. I've been trying to book a room for my son, and he eventually opted for Wimberry at Ranmoor. Was looking for approx 2 weeks and there were options at Crewe flats, Endcliffe Vale flats, Endcliffe Crescent houses, and occasionally rooms in Howden. When one flat fills they seem to release some new options, but pretty sure there's still alot of availability in Endcliffe if that's what you really want.