My back of the envelope calculation puts the weight of the kit at around 3200 g, which means postage would be around £20 if split into two Airmail small packets. I guess that leaves me out
I think the rear upright lower bolt will be shorter. Upright - 120 mm. 2 bushes: 100 mm. 2 washers - 3 mm. Nylock nut - 12 mm. 2 more spins of the thread - 3.5 mm. Total: 238.5 mm. Seeing as this is the bolt that interferes with 14" steel wheels for some people, I'd keep it at minimum.
I would also suggest adding front upright strut pinch bolts, M12x45, to the kit.