I have a single 50W LV Halogen downlight (max 60W dimmable transformer)
on a 40-250W dimmer switch. The light flickers and does not dim
smoothly. I have replaced the dimmer switch and the same thing
happens.

It has been suggested that the problem is being caused by having too
little load on the dimmer switch i.e. they work more effectively when
loaded closer to the 250W maximum.

Therefore does anyone know of another solution e.g. a dimmer that works
from 20W-150W say or similar. I do want the light to dim as it is
above the bed and don't always want it on full brightness.

Thanks

Ben