I don't have a problem with daytime headlamps, and particularly when the cars are dark grey or black, and it is raining.

I have sometimes had problems with bycyclists who have very bright LED flashing headlamps aimed specifically into the motorists eyes. I see one regularly. Maybe always the same twat.

Joe, a cyclist was killed near here doing just what you said, head down downhill, flat tack, couldn't stop, ran into a near-stationary car, over the top at maximum speed, dead.
They don't seem to realise that a driver may be unsighted by parked cars, even if the cyclist can see the car roof.