My thinking is that we only used the caravan between April and end of September so this little heater should be enough. I don't think an upright 2kW convector will fit under a seat in a Designer. That's really the only place I can store one. If we did go away in Winter I would buy a 2kW convector.
The fan heaters are too noisy for me as I wear hearing aids. So it's a chice aof a huge heater, a noisy one or a bright light one. On balance the quartz is the best compromise for me.
We have an upright 2kW convector in the garage but, like many of them, it has a broken leg so won't stand up. That does seem to be a weak point.
We have to have EHU if we want heat unless we buy a gas heater and I wouldn't use one inside the dandy. The new improved Dandys don't have gas heaters. However, I really cannot see us ever not having EHU. We only did it once in 15 years of caravanning and that was because we couldn't get an electric pitch.