They do have a room stat fitted to the unit (the Kickspace and other
models
do not) . An external stat can be fitted for better temp sensing, or temp
and timing (programmer stat).

It was my understanding that only the Loline (heating only model) has a
built in thermostat, whilst the Hiline requires an external one. Am I
mistaken?

The Hiline is much more suitable than the Loline for most conservatory
installations due to its use of wasted space above the door to the house.
The Loline would require precious low down wall space, which is often of
limited supply in a conservatory or made of materials not suitable for
mounting heating appliances.

Christian.