Senecio and its allies are infamously challenging to key. However, I'd be quite surprised to see S.interpositus in tall montane forest. It tends to occur in lower communities. It looks like this Senecio interpositus (A Fireweed)
@Tapirlord well then, that is one I've genuinely never heard of, cheers! And yes, Senecio tends to do my head in and this was the closest match in the key. You're right though, looking at your sightings (which I couldn't do up there with poor reception), it's not a match! Thank you