RE: Heater Question
I don't have a Dax but this may help you to visualise the mini heater system.
For fixings there is a stud at each rear side which will probably require you to make up a couple of brackets and a horizontal plate sticking out of the front (above the controls)
Water - one in, one out on the right hand side.
Controls are simple - a slider for heat distribution and a fan switch.
Options for the slider are keep it (not the best looking), adapt for cable operation, or I think there is still an electric servo available from RS which can be used.
Experience enables you to recognize a mistake when you make it again.