Got this through the post today...
Only 6 working days from ordering, pretty good from California! Will get it fitted and see if it was worth it.
To any other manual drivers, having now driven for a week without the clutch assist spring fitted I can thoroughly recommend it, the clutch pedal feels normal now, really smooth in action and the car pulls away better as I used to get some lurching from standstill. And it's free! Just bear in mind that you are fully committed once it's out as getting it back on would be a nightmare but for me, definitely staying off, well worth doing