For long trips in my M3W I take in no particular order:
Metric ring spanner set plus 24mm and 36mm spanners, 3/8 socket set metric and A/F, large adjustable spanner, mole grips, Allen keys metric and imperial, couple of screwdrivers, tyre levers, spare inner tube, tyre inflator, scissor jack, large plastic cable ties, large metal cable ties, gaffer tape, spare cam belt and dowels, spare throttle cable, spare rubber bobbins, used to have spare rectifier until I used it, mobile phone and insurance.
All of that fits under the bonnet.
