Consumer rights - faulty product

[Igmum]

Hello wise mumsnetters, just wondered whether anyone knew the answer to this since Google has not helped!

I bought a small electric oil filled radiator. It developed a fault just before the two year warranty ran out (phew). Contacted the company via Amazon, they were great and replaced it (slightly different model but no problem) with no fuss at all.

That was October. The new heater stayed in its box for about a month, been using it for about a month. It has now developed a fault. Contacted the company and they say that, because it is a replacement, they will not replace it since it is outside the warranty period of the original heater. I can see that, even though it is well within the six months' consumer rights grace period for this current heater. AIBU? Does this not apply because the heater is a replacement?

Thanks for reading