I finally got round to building a workbench and installing the lathe. (one of the benefits of lock-down I guess!)
Aligned the bed (using Rollys Dad's Method - works really well!) So I find the lathe is very accurate, turns to within a couple of tenths at either end of a test bar!
I think the spindle nose must be non-standard though. Are most SB9's an MT2 internal taper and a 1-inch x 8tpi thread? Mine has an MT3 internal taper and the thread seems a very peculiar size; 10 TPI and a OD/ID measured at 1.280 and 1,150 inches. 60-degree thread angle. Anyone seen similar before?