How do you change heater matrix unit on vauxhall zafira?

You have to pull out the dashboard, and everything in it. Then you have to remove the heaterboxes in elements starting with blowermotor and working your way in. be very carefull not to break it, the plastics are not that strong. There is a retainingplate in the enginebay that holds on to the top of the hosemounting for the heater matrix. Be sure to get out all bolts before trying to remove the heaterboxes, and mark all wires before stripping them. it´s a long process but it can be done in you own garage, if you have the patience for it.