You shouldn't ave to pay more than £20-£30 for the heater control panel. There are quite a few going on around in the forum atm.
As 960kg has already said, if your blower is constantly on, then most probably it is the resistor which is located behind/under the glovebox. Volvo part no. 30864189
You can either get a replacement resistor or get the transistor MJ802 and soldier it n the resistor unit
MJ802 transistor:
I have a spare resistor that you can try on your car, but I will not be back in the UK until next Sunday,
Have a look here:
http://www.volvoforums.org.uk/vbarti...e&articleid=68
here:
http://volvoforums.org.uk/showthread.php?t=60381&page=3
here:
http://www.volvoforums.org.uk/showthread.php?t=137680
and here:
http://www.volvoforums.org.uk/showth...ght=transistor