Just replied with this to Wadey:
I've been doing the following over the last 10 weeks and found it really good:
5 min warm up
1 min sprint followed by 2 mins rest = 1 set (Started off doing 3 sets and do 6 now)
Then 5 min warm-down
In the sprints have been getting my HR up to around 75-80% and on the rests between it returning down to around 50% ish (maybe a bit less).
If you're doing it on the bike (in th gym), the ones at my gyms have adjustable resistance between 1 and 25. I was warming up/resting on around 8-10, then sprinting on anywhere between 17-25 (not so much a sprint on 25, but stomping on the pedals). Think this may be hard to replicate if on an actual bike on the road, but could be done on a turbo trainer?