Sent Series X in for repair, UPS lost Replacement. Help!

Back in November last year my Series X arrived on launch day but was unfortunately not working, so I arranged with Microsoft to send it in for repair or replacement. All was going well and I received an email to say that it had been repaired or replaced and that it had been shipped back to me.

The expected delivery day came and went with no sign of the console, so I tried contacting the courier, UPS, to see if they could help. They looked into it and admitted that the item had been lost and that I should contact the sender, Microsoft Repair Centre in Frankfurt, Germany and also that I should start a claim myself with UPS. They said that as I was the recipient and not the sender they would not deal with me directly but that I should make the claim anyway, which was what I did.
Since then I have tried countless times to contact someone at Microsoft who can either send me a replacement or issue a refund for the value of the console, but every time I call Microsoft Customer Services nobody seems to be able to help and I get passed around from one department to another and eventually they give up and tell me they they have "escalated" the issue with the "Offline Team" and that they will get back to me. So far, I haven't received a single communication from them in any shape or form, no acknowledgement whatsoever.
UPS fully compensated Microsoft for the loss in late December 2020 and I would like to find some way of getting in touch with Microsoft so that I can request either a replacement console or refund that I am owed. So far it has been like banging my head against a brick wall.
Does anyone have any suggestions as to how I might get things moving with this? I'm based in the UK, in case that makes a difference.

:)