Old favourites in the Crowborough area to try:
Kidds Hill - from Coleman's Hatch to the top of the Ashdown forest. You may require oxygen. The humps are even more fun on a motorbike.
Castle Hill (Rotherfield)- Accessed from Steep Hill, Jarvis Brook (Crowborough) Gets steeper and steeper again after last corner- You often spin the back wheel on the wet leaves and moss under the trees!