Cyclocross - CX and SSCX races and training

Hmm - I like the theory of them, but the 60% on road doesn't appeal greatly.
If i'm on knobbly tyres then I want to be off road (for at least 90% of the ride)

Has anyone done the South Downs Way on a CX bike? tempted to try it one summer (or at least a good portion of it)

I would like to ride Winchester-Eastbourne on the South Downs way in 2014, let me know when you are free.