My list:
Tesla roof bars £430 (you can get cheaper 3rd party ones but they don't look anywhere near as good.)
Tesla console trays £18
Dog seat cover (because apparently I can't shut the dog in the boot)
https://www.amazon.co.uk/gp/product/B0844PYP66 £30
Underseat vent grill covers
https://www.amazon.co.uk/gp/product/B08TWWT942 £13
3d Floor mats
2021 Tesla Model 3 Floor Mat 3D All-Weather Anti-Slip Waterproof Full Cover Floor Liners Set Carpet Set Compatible with Tesla Model 3 2021 : Amazon.co.uk: Automotive £122
Boot liner
https://www.amazon.co.uk/gp/product/B08JLRF6D3 £55
Under boot and froot mats
https://www.amazon.co.uk/gp/product/B08CMR424C £45
Jack pads
https://www.amazon.co.uk/gp/product/B097XJKKBP £15
Cup holder insert (mostly in case of spillage)
https://www.amazon.co.uk/gp/product/B09536JFLZ £14
memory card & usb adaptor
https://www.amazon.co.uk/gp/product/B07P4HBRMV £43
Mini compressor
https://www.amazon.co.uk/gp/product/B08M93DPDV £29
Dynaplug tyre repair tool
https://www.amazon.co.uk/gp/product/B00LM7CSVE £70
Door seal kit
https://www.amazon.co.uk/gp/product/B07R13DYYY £30
Pedal covers
https://www.amazon.co.uk/gp/product/B085L8DDTN £15
Boot side divider
https://www.amazon.co.uk/gp/product/B07ZNBTQGB £14
HD screen protector
https://www.amazon.co.uk/gp/product/B07KXR6QH7 £19
Wireless controller adaptor (to stop my son chewing the tyres up playing beach buggy)
https://www.amazon.co.uk/gp/product/B074KX4225) £20
Also Usb C to lightning + Usb c to Usb c cables for use in the back and the devices that don't do wireless charging,
+ I already had:
Wash stuff bilt hamber auto-foam, auto-wash, auto-wheel + foam sprayer for jet wash, wash mitt, buckets with grit guards, auto-qd (as drying agent), clay bar, carnauba wax, microfibre cloths
Thule cycle carriers which should fit the Tesla roof bars (the T nut size is a standard right?)
Really tempted by ceramic coating so the paint stays in good condition for a few years (resale value), but not sure about the logistics of dropping the car off and leaving it for a couple of days.
I'm not going to add it all up