To me, a Jubilee clip is just a hose clamp.
Kevin suggests a Crescent wrench; adjustable spanner to you (or in London, an adjustable Judy Dench?) Recently, I bought a Knipex pliers-wrench. I think that it would be ideal for the truck tool box. It will replace Crescent wrench and pliers although it can't cut wire.
To your list, I would add rags, gloves, multi-bit screwdriver, spark plug wrench.
You mention wire - I would take a small roll of rebar tie wire. Great for temporary fixes.
