Bit late reading this one.
For me, number 1 is a Smartphone followed by breakdown cover and then in the boot fan belt(s) , points, fuel filter (only if there is any doubt about the condition of the tank) , fuel pipe, fuses, bulbs, water, oil, brake fluid and windscreen washer fluid with possibly a spare wiper blade in winter. Assuming you have a 'travelling' tool kit ensure you have some wire ( strong enough to replace an exhaust bracket say. . Beyond that there is a rule that says that if for example you carry a spare dynamo, your dynamo will NEVER play up when you are away.
Bon voyage.
Chris