If not done previously turn off the outdoor water supply at the stop valve and drain the pipe between the tap and the stop tap.
Insulate outdoor taps with proprietary lagging.
Empty hosepipes, wind them up and store under cover.
If the cold has made the hose too rigid to coil easily, try running warm water over/through it.
Week 2 onwards:
Take the opportunity when you can to wash plant pots and trays in preparation for the new season.
Replace any damaged pots and trays.
Check over heating equipment and adjust as necessary.
Order seeds and composts if have not already done so.
Commence clearing away dead/dying annual bedding and fallen leaves as necessary.
Prepare / protect outdoor containers containing less than hardy plants.
If you are finished for the season with any outdoor taps or water features turn off the water supply at the stop valve and drain the pipe between the tap / water feature and the stop tap.
Week 46 onwards:
Insulate coldframes and greenhouse with bubble wrap insulation.
Similarly wrap containerised plants as necessary.
Ensure that any trees / shrubs that may be exposed to high winds are well supported.
Repair any broken glass to prevent draughts and the ingress of winter snow.
Make certain that all exposed water pipes (including drained ones) and taps are lagged, as severe cold can creep along metal pipes and cause problems indoors.
A stop valve should he situated somewhere along the spur line connecting the indoor mains and outside tap, enabling the pipe to be emptied by means of a drain plug.