Not exactly an accessory (more like a mod) but negates the need to buy any of the rechargeable magnetic mounted LED lights and is much neater (don't judge by the initial photos, I intend to tidy the installation up

).
Although the rechargeable LED lights provide a lot of luminance, they tend to turn on when it is bumpy and sometimes fall off their magnetic strip mount unless using industrial strength 3m two sided tape.
I have decided to add a second LED boot light on the other side of the car using these two parts: x2
Saborway LED Footwell Light foot Lamp with Cable Wire harness and
LED Luggage Compartment Trunk Boot Light
Daisy chained the two cables (you will need two as one is not long enough) and passed them through the left plastic grill, below the spare wheel foam insert and up the right hand side grill to the gap where the optional (for VW and Skoda) Magnetic Rechargeable LED light is housed (more on that later).
The LED unit slots in perfectly width wise but leaves a small gap at the bottom and a bigger one at the top, I am using a bit of cardboard currently to plug the gap and intend to find a more permanent solution when I have more time. I am also going to use some spare velcro to tidy up the cable either side with a view of routing it behind the trim pieces if there is a way (if anyone tries it and manages to find a neater route please share).
The neatest solution would be to install the following x3 VW parts:
3T0 947 509 9B9 Dock
5L6 867 559 82V Frame Case
3T0 947 417 B 9B9 Magnetic Rechargeable LED battery unit
However: a) they are expensive (£135! altogether) and non returnable (as they are special order for a SEAT) and b) VW/Skoda owners are reporting that although the LED unit is supposed to work as a secondary boot light (as well as a removable rechargeable mini flashlight) it doesn't.
So in my mind, spending £135 is too much to risk for something that might or might not work.
Initial installation photos below: