Cruise control doesn’t use the brakes (I think). So it should cut the throttle going down a steep hill. And also change down for engine braking.
Not sure how eco mode changes things, but it doesn’t use engine braking so would assume that it could run away down hill under cruise control.
The illumination round the power outlet is only activated when the headlights come on due to low light.
If the headlights come on due to rain, then the power outlet light does not come on. Although in both cases the illumination for the lights knob comes on.
This may all be unnecessary...
SD nav - lots on here about that. Probably a dealer install £500 issue as you’ve been quoted.
Wipers - are you sure the intermittant setting on the top of the control arm is not on the left, which makes the wiping very intermittant.
Has the car had an accident which meant the dashboard etc has...