Rear brake caliper piston replacement

[Storm]

I got a new rear piston from Camskill but there is nothing inside it. The handbrake screw mechanism needs to be removed from the old one and put into the new one but I have no clue about how to get it out

New piston is easy, it comes with a circlip to hold the mechanism in but the old one is the original piston from 17 years ago and it looks like it was pressed in then the piston wall punched to hold it. How the hell I am meant to get it out without buggering up the innards I don't know!

Any advice would be appreciated.

I have polished the old piston for now so everything is fine but I don't see the point of having a shiny new bit I can't fit to the car

[Storm]

I thought here of all places I would find the answer!

Instead, I spoke to the guys at EBC who advised me that I needed to cut the old piston in half to get the handbrake mechanism out!

Grinder and cutting disc it is this weekend then!