I had the Webasto 2000STC fitted by Slidepods. It’s my first experience of a diesel parking heater, so I can’t really compare it to the factory fitted option, or any alternative. I’m happy enough with it though. I had a temperature sensor fitted just above the control unit, on the passenger B-pillar. It takes a while for the thermostat to settle down, if returning to a cold van in the evening. I think this is because the thermometer is affected by the cold frame of the van. It’s fine after the van has warmed up, however.
The heater would be quite noisy to a light sleeper (or neighbouring tent!) which we’re fortunately not. It sounds a bit like a turbofan jet engine spooling up. I’ve reduced the default fan speed to 1/3 to reduce the noise. Given that the heater is very powerful, I wish it had an even lower/quieter setting.
It’s great at warming up and drying the van though. I reduce the thermostat at lights-out, so it rarely kicks in at night. The dogs aren’t keen on the noise/dry air/smell but welcome it when they’re wet & cold.
Another slight negative is the exhaust smell outside the van, but if it’s cold enough to have the heater on, then it’s unlikely that anyone is sitting around / sleeping under the stars nearby!