Customer doesn't want Triton to come out to repair - wants a replacement new one.
http://www.which.co.uk/consumer-rig...erstanding-the-sale-of-goods-act/your-rights/
"You have the right to get a faulty item replaced or repaired, if you're happy with this (or if it's too late to reject it). You can ask the retailer to do either, but they can normally choose to do whatever would be cheapest."
The key here is the reference to consumer. I presume your customer is a consumer (i.e. not a developer), but you were not a consumer when you bought it from your supplier, you were a trade buyer so the consumer protections do not apply to you (i.e. you are the retailer in the last para quoted above).