After spending many frustrating hours upside down cursing and swearing I eventually managed to replace the heater fan speed resistor on my wife's car. Question, why are they where they are, only reason I can assume it is for the airflow to cool the coils. Is that it?

Yes, they need the airflow to cool them so are right next to the fan.

Thanks

What car was it?

I've done a few of these, quite a common problem.

Ive just done this on my Renaultsport Megane 225. It was an easy job.....5 torx screws and the glove box is out and its easy to access the back of the fan where the pack is housed. I was lucky that i just removed and refitted the relays and the resistor pack and it started working again

Hi melly-g I changed the resistor on my Renault Master van without a problem but my wife's car is a Citroen C4 coupe and that was a pain.