Clean water butts by emptying them and spraying out with a jet nozzle on the hose or scrubbing them with a brush. They will then be ready to catch the extra water expected at this time of the year.
Drain out standpipes and irrigation lines to avoid damage caused by water freezing inside them. Roll up and store plastic hoses.
Mend any broken or rotted pieces of wood in the structure of the compost bin, or in slatted wood garden furniture, if not done last month.
If you have not yet fixed or replaced any shed roof leaks, broken glasshouse panes, or worn glazing putty and lost glazing clips, then now is your last chance to do so before the greenhouse is full of tender plants for overwintering. More on cleaning the greenhouse.
Get your lawnmower, hedge trimmers (plus any other power tools not needed over the winter) serviced now in preparation for next year.
Turn the compost heap to speed its decomposition.
Consider building a post and chicken wire leaf pen for autumn leaves. They turn into leafmould - very useful as a soil improver or as an ingredient in potting and seed composts.