Most of my photos at the hairpin were taken with my 70-200 F4 lens, which is very nice to use. Light, fast focussing and you can go from 70 - 200mm with a few inches of wrist movement. Another one worth consider would be the 70-300 lens, which also has IS built in and has a bit more reach.
I've also got a 100-400 which I use for the longer range shots, generally using a tripod or monopod as it's a bit on the heavy side unless you are used to it like Neil is
You are welcome to try out any of my lenses if you want yo meet up somewhere at some point ?
John