[Fastera]

A £320 Nintendo switch , could the battery leak method work on curry’s ? If they asked for pictures I could say I threw it in the bin and show pictures of the empty box in the bin

It might work but showing empty box in the bin would likely not suffice. They may request for you to dig it out and photograph the actual product.
Fellow SEr in another thread mentioned that providing them with receipt for disposing of it properly worked for him.

If you have a good Amazon account you might find it easier to DNA from there. Currys will likely ship via DPD so DNA will not be possible from them.