How to remove coventry easychange chuck/toolholder

[Rabs]

Hi everyone,
I've hit a hurdle with the refit of my Conect Contour Major mill. It is fitted with the Coventry 'Easy Change' system. The toolholders for this are very expensive and the chuck protrudes a long way from the spindle. On a machine with a very modest Z travel this is quite limiting and I would like to remove it.
Unfortunately I can't work out how to get the b****y thing off! I've attached a few pictures of each end of the spindle and if any kind soul could point me in the right direction I'd be grateful.



At the top of the spindle assembly is a bar with flats for a spanner. I originally thought that this might be the drawbar but now I'm not so sure. The hole in the top of it is blind to about 10mm, it doesn't go through the assembly. There is a dust seal at the bottom of the picture, which I imagine wouldn't normally be around a drawbar because you'd expect it to move up and down?


At the bottom there is nothing obvious to release the holder


There is one circlip here (sorry, bad photo), but I can't see that being relevant because there's no way a circlip could give the required force to pull the holder into the spindle taper. I suspect that this is part of the toolholder chuck itself to retain the release collar.


Both easychange holders currently sold by coventry have a tapped hole at the top for a drawbar and I can't see how it can be anything other than retained from the top with a drawbar. But try as I may I can't get the thing to unscrew with a spanner at the top and a strapwrench around the collar at the bottom. The machine was pretty gummed up when I got it so it might just be stuck on hard but I'm hesitant to try anything more aggresive until I'm sure that I'm applying force to the right bits.

Any thoughts anyone?