I have a C20XE engine with type 9 gearbox using a Caterham bell housing, its a cable operated with what i assume is at standard release bearing and arm.

When I depress the clutch I get a banging noise, its not not engine speed related, when the bang happens the clutch drags a little.

I'm assuming the clutch arm is catching something, but can't see much through the bell housing hole, any ideas?

Cable end nipple sliding / moving in the release arm?

It could be that the clutch release arm is going too far. Mine did that until I changed the pedal ratio.

If you have a pedal stop, adjust it out to reduce pedal travel. If not it might be worth installing one or changing the pedal ratio.

As above,possibly over throwing the clutch.

So the spring fingers are touching something on the clutch plate as it's spinning

Don't think it's down to the clutch adjustment, today I tried backing off the adjuster so could only just get gears, but still it happens. Seemed to happen worse when hot, but since found a bad oil leak from the rear engine seal, seems engine will be coming back out.