To save your heartache and stress Tim could you not have a member of the family on insurance or to get them to become an appointee. so they can handover and collect your new car for you, just incase Mb/dealer don’t allow a home handover.
I’m thinking of you to save all the stress its putting you through, which don’t get me wrong I fully understand your situation on the matter.
The other thing is all the stress/anxiety involved getting a legal team and battling it out with MB and the cost involved to yourself unless you can can legal aid. Going this route would drastically help your case if you new of others on the scheme that had been promised an at home order/handover and it never materialized and willing to stand with you as you go through the legal battle.
My only other advice is screenshot any info Mb has on their site that suggests an home handover and a documented timeline of calls/emails from you and Mb on the situation. It may also be worth getting your MP inolved.
I wish you all the luck and hope you get what you want, but please don’t let it be at a disadvantage to your health 🙂