We decided to go for the tethered wall box after much debate and for carrying a type 2 cable stored under the boot cover, with the space saver.
Storing the cable from a untethered wall box, in clear view every time the boot is opened, plays havoc on my OCD

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The tethered box and a carrying a type 2 car in the car, is a more expensive option of course, but I did have a true concern, that with the untethered box, it would be likely that I would to do the following.
After charging at home, I would remove the cable from the car, hang over the box, then in a hurry, take off and leave the cable attached at the box, at home.
No problem with this, until you need to charge on route or at your destination.
Then you suddenly realise you have left it attached to the wall box - Dooh !.
I do agree, that the untethered wall box does look much tidier with no lead attached, but our tethered wall box is inside the garage, so is completely out of sight anyway.
The Granny unit does have its usage though.
When one of my close relatives had his ZS EV - he called me one morning in a bit of a flap.
His ZS EV had refused to take any charge from his wall box, he had tried several times and it failed each and every time.
He only had about 10 miles of range remaining and the dealer was too far away.
I asked him if he had tried the Granny unit ?.
He had no idea what I was talking about

.
I explained where to find it and then how to use it.
Straight away, the car started charging

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When the installer checked his wall box, it turned out to be a fault in one of the type 2 cable sockets.
He had coiled the cable around his untethered wall box and moisture had entered one of the sockets, even though it had the so called weather proof protection boot attached !.
He opted to replace the cable and install a hooded shield over the wall box.
Had he not had the Granny unit as a fall back plan, then he would have been well and truly stuck

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Lesson learnt - always have a back up plan.
Granny unit for the win

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He has a nice Volvo EV now that naturally, did not come with a Granny unit.
I strongly advised him to retain the unit from his ZS EV when is was declared a total loss by the insurance company, after it suffered a huge rear end collision, while they were stationery in traffic.