Welcome - that's a great colour!
Haven't done that mod but keep eyeing it up, it's very much part of the iconic look of the car. You can also see it as useful maintenance for gradual warping of the older tail light units. Also note that the rear light gaskets give up eventually and start to leak water into the boot, so make sure the kit comes with new tail light gaskets - ATR should sort you out
Does that kit come with the LED third brake light strip to be inset into the spoiler? Most UK cars had the third brake light deleted and a plastic blanking strip instead, but still have the harness for the light if you want to fit one.
To see that set of lights flash past on a dark motorway will take you right into a Tokyo special stage - it's a public service you're doing there!