Right hand drive car of that makes a difference.

When the fan is on 2+ there is a chirp or a squeaking noise in tune with the fan from behind the dash. Giving the dash a good thump over about the glove box sorts it out for a couple of minutes.

So there's a fan back there, how do I get at it. Does it need lube or what's it complaining about?!

 

You are going to need this: M A Z D A

HEATER, VENTILATION & AIR CONDITIONING > SYMPTOM TROUBLESHOOTING > NO.9 NOISE WHILE OPERATING A/C SYSTEM

And depending on what part it ends up being, the BASIC SYSTEM category has all the repair info points.

 

Nice one.
But from reading the link everything, including the dash, will have to come out in order to get to the blower unit.

In my experience with other cars you often don't need to remove all the bits they say so I think I will just start digging behind the glove box and see if I can get at it