Firstly thanks for your replies to my other recent posts; I now have1
SDS driil and frame fixings on order. Now on to the project itself -
replacing a side hung timber casement window. I have the process down
as:

1. Remove glass
2. Remove old frame*
3. Offer up new frame
4. Wedge frame in place ensuring it is square
5. Fix frame through sides with frame fixings
6. Glaze
7. Seal around frame
8. Make good inside

* My question is looking at the frame on the outside it is resting on
the layer of mortar above the soldier bricks - how do I remove the
frame without pulling soldier bricks away with it - how do the double
glazing guys do it?

As always any advice greatly appreciated.