To continue with this heater problem....

I found a thread elsewhere which suggested it could be the "Heater Control Valve" which it says is a common problem with Pumas. I suggested this to the garage but they said they fitted a new one of these shortly after we got the car and it had a water leak (two pipes loose under the windscreen).

They've said they will try changing this valve to make sure it wasn't as faulty one, but, failing that, they suggest the Heater Matrix might need replacing. A big job they said - £95 for the part but have to take all the dashboard out to do it.

Does this make sense?