THe brass bushing had fallen apart
At least, I think it's brass. Managed to make a wee replacement spacer out of some stainless tube so that's it back to normal, wee bit flappy as I didn't get the size quite right, might need to have another go. Wasn't expecting that, to be honest I didn't think it was just seized up as it was so sudden, went from fine to knackered in one shift, which made me think something had broken. Which it had, but I didn't think it'd be the bushing.
Sorted now anyway, cheers folks