I get what everyone’s saying about it being the shop’s responsibility but to me it seems like there’s going to be a difference in the way that a shop who sourced the part through the distributor and the shop who sourced the part from an online retailer would deal with a problem.
A shop who sourced a part through the official distribution channel would be quite happy to send the part to the manufacturer who would then say yay or nay to a warranty claim. There’s probably not going to be any need to resort the the sale of goods act.
A shop who sourced from an online retailer on the other hand would not be able to send the part to the manufacturer (I assume, this is the part I’m not sure about). Therefore it’s up to the shop whether they give me a refund or not. Since they’ll be out of pocket if they give me a refund it would be fair to say that they would be far less likely to say the part failed because of a manufacturer defect. Then you will have to resort to the sale of goods act.
As a consumer it would be nice to know where the part I’m buying was sourced.