Now working with 2 speeds! Think there may be an issue with the switch….. everything works fine until I put the switch in the housing and tighten the screws that hold it. Then fast speed disappears….if I slacken one of the screws, just a bit, then two speeds return. It all back together and I have two speeds and unusually for me, I don’t appear to have created another problem. Only logical conclusion regarding tight/slack screw is earthing? Anyway, for now, all’s right with the world.
Unlikely to be anything to do with earthing (which the switch doesn't need). More likely a wobbly contact in the switch.
It could be that the metal body of the switch is not properly gripping the plastic panel with the switch contacts mounted on it.. Or the screws are too long and blocking the switch movement to the fast position by acting as an accidental end stop for the switch. I seem to remember the screws are quite short.
The screws in mine are longer than that, about half the length of a domestic plug fixing screw. The indicator side has a couple of random ones that fit.