In future TB I suggest you always communicate with them online then you should receive the service we all expect

But in scenarios when there isn't an online option - such as this one, the courier claimed they had delivered, but hadn't.
Clearly not Amazon's fault per se, but if they won't tell me who the courier is (beyond it being "Amazon Logistics", but that's a generic cover name for the local, cheapest couriers going, to whom they subcontract), or chase it on my behalf, what can I do? Sit around and accept that my £250 item may or may not ever turn up?
I had no joy from Amazon - not even a guarantee that it would
ever be delivered when I asked, nor would they give me the 3rd digit of the courier's phone number (or the 6th - and I gave them a multiple choice option of 4 digits), I genuinely do not believe they wanted/able to help, as it was off-script.
I've had similar trying to resolve Kindle troubles, if its not a simple query (that could be done online), they make every effort to make it difficult, probably not on purpose.
In this case, I guessed the courier (there are a fair few in Milton Keynes (Amazon's tracking said it was delivered from MK depot)), rang them (their number is clearly published on their website), explained the situation (after they said I really should talk to Amazon), and the item turned up about 90 mins later, and has now been fitted.
Reading between the lines, I suspect the courier claimed delivery on the promised day in order to meet stats/KPIs. I know Yodel are a bugger for this. Yet Brackley is hardly the arse end of nowhere, its a small market town with around 8-10,000 residences...