surely only those who are totally confident at hand flying in IMC should switch the autopilot on?
Quite so. If you're depending on the autopilot, what happens when it stops working while you're in the clag? There have been fatals because of precisely this - pilot depends on autopilot, a/p dies in mid flight, pilot rapidly does the same. Not healthy.
It's certainly going to be tricky to pass an IPC or IR checkride just relying on the a/p.