No, not Peter Fogwill, but one of his happy customers here.
I use the "autobrush" which means I save loads of water. It's not a sensor as such but a "bar" or "rod" which goes the length of the brush and overhangs it slightly. It is connected to a tiny valve which opens or shuts as you tap the bar end (protruding on either side of the brush) between windows.
When working downstairs you just use your finger to push the bar across at the start or finish of each window.
Peter has recently upgraded the switch to a meatier version and it is even more positive than the original.
It saves both time and water - what more could you want?