Hi,
Yes, I did some more digging last night, it’s a universal motor so what I can do is rectify the current to DC upon which PWM control is a million times easier.
The internal controller at full speed just shorts out the potentiometer by using an inbuilt switch, so what I’m going to do is remove everything from inside the body (except the smoothing capacitor) and relocate them remotely.
Then I switch out the power button for a solid state relay and implement a design similar to this: www.thingiverse.com/id/AC-PWM-Dimmer-for-Arduino
In the end realising it was a universal motor simplified things immensely, though the initial problem is still an interesting one to solve someday. :)