Ok team. An update!
My parcel was too big to fit in the original drivers vehicle (10*10*5cm - the parcel, not his vehicle) so they've given it to a different driver with a bigger vehicle...
The nice man on live chat couldn't explain the size or the original driver having had it in his van to "attempt delivery".
But he did promise (and I made him explicitly type that out) that the parcel would be delivered in 1-2 days.
An hour later I got an email with a new tracking number saying delivery would be in 5 working days....
New tracking (amalgamated with old tracking): https://www.myhermes.co.uk/tracking-results.html?trackingNumber=5726382099786659
Supposedly they tried to deliver 3 times over the weekend. Hmmmm.
Can you see what I mean when, at the start of the thread, I said that I find it very difficult to get MyHermes to bring parcels to my house?