My next vintage lens arrived. The Mamiya-Sekor 50mm f/2. This lens is a bit softer (I assume its the f/2) with very smooth operation, though I find it a touch more arduous to focus than the Sigma Mini-Wide II, despite its lighter weight (probably also the f/2 given the slightly narrower band of focus). But its a beautiful lens. I assume I'll start using this for portrait shots alongside the Canon EF 50mm STM f/1.8.
I also got the Diana+ fisheye, which on the APS-C crop-sensor is actually an 80mm telephoto - but - it gives an almost as good as the Holga (not quite) at a more usable field of view as the 60mm Holga is 96mm on the APS-C crop sensor.
As usual, I am looking forward to playing with this more!