Am now looking at going out at the end September as the start of October sees 3 days of unbroken public access to the track.
As this year has been pretty mild we should have pretty good weather - but be warned if it rains it is not the place to drive heroically - it is much better to tour round when the track is slippy.
I've driven the track in late October before without any problems and it is actually quieter (and therefore safer) as the bikers tend to be thinner on the ground.
This could be good!
S