We are now metered for water as well as the gas we use to heat it. So even more reason not to waste hot water. You may be able to save without spoiling your experience in the shower by fitting a Challis Water Widget.
The device fits easily between most shower heads and their hoses. It works by aerating the water as it passes through, maintaining an invigorating flow whilst reducing hot water consumption.  
The Challis Water Widget is designed to reduce your shower head flow to 5 litres a minute - a flow rate which has caused no complaints from fussy teenagers of our acquaintance. If you already have a low-flow shower head or an electric shower then you do not need to fit one. The widget is currently available for a small charge from Challis Water Controls and can be ordered here.