bristan thermostatic shower cartridge stuck?

I am attempting to change the seal kit on the cartridge kit, but cannot get the catridge to come out...I have removed heat contoller, shower float control, 2x grip scews, plate and nylon seal. I then put the float controller and brass circuit back.....when then attempting to pull out the catridge by using a screw driver....well that's where I am stuck....the catridge turns, but would not pull out....it is stuck...I have used WD40 for 24hours....still nothing.

Any ideas??? is there another bolt somewhere which I missed?

Christi
October 2012