Odd question, but have any of the bulbs gone on your climate control panel? On mine, the bulb behind the middle dial (fan speed) had gone, and replacing it (sort of) fixed it.
I can't remember who on here suggested it first, but after reading the bulbs sometimes cause heater/air con issues I decided to replace 2 heater control bulbs that had gone on mine et voila: heater works properly again!
I always had aircon and I live in southern Spain so no heating is just an annoyance in winter months, which is why I didn´t get round to attempting this fix sooner.
My radio unit refusing to release didn't speed things up either. (one of the springs that keeps it in place was bent out of shape, now fixed too)
Anyway, went from annoyed at paying crazy dealer price for the tiny bulbs (over 10€ each, ouch!) to being pleased with a cheap heater fix.
Also noted that the bulbs from the dealer had a little resistor on them, which the original ones didn't have.
My wife's 147 has 2 bulbs gone too, but no heater issues, so I'll go ebay cheap bulbs to fix that.
Thanks again to the collective alfaowners forum wisdom!