As Ciara has said, the Bike Interval Training is starting on Wednesday, it is only for 3 weeks, so please give them a go. I would particularly encourage those who have not tried them before. Basically you do the intervals in a group of similar speed and ability and only take a turn at the front for 30 secs. The Interval bursts are on a 2.5 km course with 2.5 km recovery.
The more people that take part, the better the groups work.