Hi All.
Just to add a note about the rear rollers:
The rollers on my "P2" Qualcast (gravity-fed carby) consist of three rollers, as in the above pictures, but the outer two are tapered.
The inner central roller is a true cylinder being 45mm in diameter.
The outer pair are 45 mm at their inner end and are 36 mm at the outer ends.
Not sure if this is a feature of the P2, but I can be reasonably sure the rollers haven't "worn" that way. The measurements are too consistent.
And the rest of the mower is in very good, unworn condition. I have had it for more than 50 years. Not sure of its history before that.
Jeff