Visit a few aftermarket warranty websites and look to see if they class a Heater matrix as ‘wear and tear’.
Start with warrantydirect.
Why? This will give you a good idea what these sort of companies would class a heater matrix as.
Could you clarify for how long after purchasing the car did you notice the heater matrix problem (not just the smell) but also at what date/days in did you notify/agree there was a leak/issue with the heater matrix with this dealer?
Do you have any communication written down?
I’ve successfully rejected two cars due to faults. Anytime I have had any issue with a car bought from a dealer I have used fax or email as communication (or as backup ‘as discussed on the phone’).
What is the year and actual mileage- could you be specific?
I’m guessing here but my spiderman-like powers are telling me you’ve bought from a very small indie dealer or someone who trades by appointment?