Subject: Re: steering stop on offside brake back plate
to complete the circle and for anyone else with a similar problem, I have had a cylindrical piece of metal fixed into the original space, after a bit of machining out of the area. This cylinder was then welded to a flat piece of metal at right angles and fixed to the back plate with screws. The cylinder is suitably drilled and tapped to take the new steering stop.
Now all I have to do is re-attach it to the car...