Re: GTV V6 Heater Problem :(
Not sure on accessibility to matrix. Heater designs have improved slightly in some cases and the matrix can, on some, be pulled out like a draw instead of starting by removing the seats and the headlining(haw haw). I've had the problem in the past and, like a radiator, found cleaning impossible, waste of time, need to fit new matrix. I must say it's probably less likely, the anti-freeze/corrosion inhibitor keeps it at bay for quite sime time, but should be changed according to the service schedule as it becomes exhausted over a number of years. We had a 145 (Twin spark 1998) on which a plastic clip broke which retained one end of the temperature control cable. The fault was obvious as the 'rotary control' went from being horribly stiff to totally limp. Meant dismantling the dash (unpleasant) and fixing the end of the cable outer to something using a decent brass clamp! I'd quite forgotten about this one till now. The 'servo' heater controls feel totally different, lovely and smooth and don't actually have limits they go round and round in wither direction for ever. That's at least how it is on our 147. I too hate cold all the time!
Doesn't say that in the manual