Managed to find some time to continue this story. Picked up a remanufactured steering rack for a good price at a specialist shop. So that'll go in once the other aspects are covered.
I made a 'bracket' out of some sheet aluminium I had around. Bend by hand and cut with some tin snips. It is now inserted in the same holes that normally hold the washer bottle (I had a spare washer bottle around from which I cut the pins that go into those holes). It is not perfect, but does allow me to continue measuring and fitting. I removed the reservoir of the pump as the remote reservoir units are only slightly larger than the bare pump itself.
Shot from below, so you can see where it might sit:
From the side a view of the top. I should be able to get the hose routed in to the remote reservoir (which would still be higher than the pump).
Not complete without trying to fit the liner back. As you can see I need to rotate the pump a bit (it is mainly the cut pressure line that pushes on the liner) and might need to move it up slightly more. Also it looks like I can reduce the tilt a bit. The bump in the liner looks significant, but that is partly due to it pushing the side away from the bodywork.
Christmas period is upon us shortly, but I hope I can make a few iterations and get it to fit. Hose routing doesn't seem too difficult (yet).