As part of her duties as my back-up team when I'm running a long distance
race, my wife may need to boil up stuff for my consumption in the car.

Because of the potential of severe midge attack, this may literally have to
be done in the car with the windows closed (so no gas or other naked flame
suggestions please) .

Would it be worth investing in a reasonably substantial inverter (and
where's the cheapest source for these) that can supply a standard kettle or
might a smaller one powering a 1kw caravan type kettle be more
reasonable/affordable.

Alternatively, are the any good 12V kettles or other electrically heated
pans worth considering. We will probably want to warm up soup as well as
make coffee/tea etc.

My car's a diesel people carrier with a reasonably substantial battery.
Would this cope with boiling a kettle every couple of hours say or should I
invest in a second battery?

Tim