Some progress pics.
I covered the side in sharpie pen, to see the sanding progress. It still needs a bit more work, but at 220grit, it is starting to look nice. The casting is good, the odd pit here and there, but they are small. This is a user plane, so whilst I may choose some nice wood for a wedge, and polish it a bit more than necessary, the odd pit isn't an issue. I presume that it is brass rather than bronze.
I have a slight issue with the bed of the blade. I have slightly misfiled it. I must have rocked with the file, it is difficult to keep it perfectly parallel.
The blade is bedded at 20 degrees. Lie Nielsen bed theirs at 18, so I have the option of sorting out the error by having it put onto a milling machine. The ends also need squaring- I can do this on the pro-edge.
I have an HSS planer blade to use as a blade, and am going to put a steel sole on it from (probably) a hard point saw. The bed is the part that is causing me concern at the moment.
The other consideration is that the cutout is not 100% square. I have the option of leaving it as is, squaring it, or opening it up a little on one side like on some wooden rebate planes. no rush on that at the moment. It is hard to measure how out of parallel it is, or is with the limited equipment that I have.