Certainly October is getting a little late in the year to be in our neck of the woods (JOG).
We get quite a few people in September, but numbers drop to virtually zero in October as the weather can be very unpredictable. The winds can be quite strong in Caithness when the weather turns and, as those of you who have done LEJOG will know, Caithness is very, very open.
I'd do it in September.