Title say sit all really...
Battery, should be 12.5 volts minimum after 2 hrs of non use. If it's less than that, consider a new battery. Diesel batteries get clobbered, and with PAS alone capable of taking 60 AMPS a good battery is essential.
Screen Wash. Use plenty of screenwash additive to prevent freezing of washer fluid. Too little and you risk blowing pipes off the washer pump or tailgate fittings.
Wipers. Check blades are in good condition. Don't operate wipers if frozen to the screen. If you do F15 will most likely blow.
Tyres. 3mm minimum tread. 1.6mm is the legal limit, but you really need 3mm or more for winter use. Check the spare wheel condition and pressure, Nothing worse than getting a puncture, only to discover the spare is flat.
Aircon. Use it now and again during winter to prevent system seals drying out and leaking due to lack of use.
Carry a bag of rags to clean lights between washes.
Edit: Have anti freeze protection level checked. 50/50 G12 works nicely