Howjado, for the time being if you don't want to loose this engineer, could you just mark his card by saying something like 'I really don't mind you charging the van whilst your here, but could you let me know in future?'
Then follow driverann's advice and check up on other engineers availability and capability.
I know we have tried to get plumbers in to service or repair our boiler which is oil fire, and found it particularly hard, ie the majority don't work on oil boilers locally, and the few that do don't seem to be very reliable.
We found one who doesn't stick to a normal timetable but does actually turn up.....eventually!! He's also a bit tetchy too, but we have cultivated him over time, and he always helps out in a crisis now!