…Will this cause the headset to bind at certain places?

First of all. Yes the headsets installed in the correct order.

I’ve got a second hand cane creek S3 that was perfect on my old bike. Just fitted it to a sanderson life (who face their head tubes according to the website). I fitted a new star nut to some new forks, and it didn’t go in perfectly straight.

Anyway, when I tighten the nut to the point where there’s no play, the headset is binding and there’s a rough noise coming from it.

no its not the nut to blame for that.

The only other thing I can think of is the crown race… gonna try and make sure it’s fully home… otherwise it’s LBS tomorrow for one reason or another

I don’t think it’ll matter, its more likely you’ve assembled the headset in the wrong order? But you say you haven’t 🙂 Have you moved the bearing race from the old fork steerer to the new?

However, I’d get a flat blad screwdriver and use it to knock the high side of the star nut down a bit.

Yep new crown race is on the new steerer. The crown race won’t seat completely flush on the steerer, if I tap it with a screwdriver on the high side the other side lifts off. Suggesting it may be bent. Can’t see how that’s happened but this might be why.

Crown race should be solid with no movement on the steerer. I’ve got a handy bit of scaffold tube with the right inside diameter I use for fitting mine, they need a good knock downwards to get them seated all the way round, you definitely don’t want it loose at all! That might be a good place to start?

its not loose, it just won’t go down evenly, might be bent?…

If your star nut needs straightening, put a bolt in it, and hit that to straighten it.