Putting this out there in the hope that it helps someone else who’s had issues with this mouse (which is otherwise pretty comfy and good value IMO). I bought it from Tesco (who I think own the Technika brand, but seemingly don’t want to support it very well).
It wouldn’t install cleanly in Vista, claiming at the end of the driver install process that the device was unknown.
From what I gather this is a general Vista USB mouse issue, but this was where I found the solution for my own problem:
In short, find the unknown device in Device Manager, and update the driver to “HID Compliant Mouse”.