I took have a 2017 Shuttle SE.
I kept the car as much original as possible hoping not to put off anyone who buys it off me when I change it.
I didn't want to pay the Van King prices so built myself a plywood shelf in the rear and use an IKEA 4 inch futon mattress over the shelf and rear seat folded forward. It's lives stowed over the shelf when the rear seat is up.
I fitted Kiravans curtains Just Kampets insulation pads over the windows, with smoke colour wind deflectors allowing me to leave the front windows down and inch without folk noticing.
I fitted a cheap AGM battery and a Renogy DC-DC charger under the passenger seat. This powers the secondary (3rd) diesel heater which is under the vehicle hidden behind the plastic protector panels. I have outlets, usb & 12v and lights off the leisure battery also.
I also fitted a single captains passenger chair and swivels to make it more convenient when the weather is grim and you don't want to have to go out of the vehicle to get in the rear.
It's enough for me to be able to use it as a camper, including cooking on an aluminium table in the middle, as most of the time the middle seats live in the conservatory.
The downside of a Shuttle is you limit the number of convertors who will touch a Shuttle, or at least this was he case when I first bought ours during lockdown.
I bought the Shuttle at the time as I wanted a camper during lockdown for everything shot up in price as a result of demand. At he time Auto trader had everything under the Transporter option except the Shuttles. Shuttles were lower milage and less money at the time. I put it down to businesses not being able to operate, due to the Lockdown, no flights etc, and having bought the vehicle of HP, so flogging them off cheap. I saw a High line Kombi at 160k miles for £24k and a Shuttle SE at £20k with only 80k miles on the clock.