I fleeced my winter/spring Cauli as you suggested in your book on winter veg.
You advise removing this in early autumn but given how mild this autumn has been would do so at this point in the season?
I would yes, although there is the odd butterfly, because they can grow through that and will benefit from the extra light. Fleece keeps around 30% of light off. Also in winter, if using any cover, I prefer mesh as bird protection, rather than fleece which risks tearing in winter winds.