Finally got her stripped down last night, but didn't want to draw any conclusions in the dark under a work light.
This morning revealed that the timing is still cock on, checked and set this time using the flat bar to lock the end of the cams and the metal pin to lock the ring gear. So, I'm now sure that the timing belt was done correctly.
The cam sprockets both have play. The inlet side exactly matches a YT video showing buggered cam dephasers. The exhaust one (where the noise mostly seemed to be coming from) was actually better, but was absolutely full of oil, whereas the inlet only had an egg cup full. Not sure if this is correct or indicates some internal breakdown in the exhaust cam.
For the sake of it I'm going to strip them both down later when they've finished draining oil, mostly to see how they work.