The heater matrix of my Suzuki Khyber was also blocked. The pipe taking water to heater matrix used to be hot while the one bringing water back from heater matrix used to be a little cold. If you are standing outside and facing your car's engine, then in my case the hot one was at left and cold one was at right. May be the pipes can be connected either way, not sure of it.
After the heater matrix service, my problem of heater throwing cold air and needle staying low, both were resolved but please note that right from the day one when my car was rolled out from factory, its temperature needle remain at around 30% position, it does not go to the middle. So if your heater is working fine and you are just servicing the radiator matrix to keep the temperature needle high then I won't recommend it as the needle looks fine to me.