Repeal all laws relating to units of measure and replace with a single simple law requiring all measurement relating to trade, government and regulation to use a single, rational system of units which conforms to the international standard or Metric system.
Why does this idea matter?
There are many different laws in our country relating to units of measure. Some, such as road signs, require only imperial units; some allow for metric as a supplement to imperial; some require metric measures only; some allow imperial as a supplement for metric.
We only use metric in schools, except that the curriculum requires children to convert between metric and the imperial system (which they're not taught about). Many of our citizens don't have any clue about their grandparents' system of measurement, and many people are working in units that they can't use in calculations (e.g. they can't remember if it's 16 ounces to a pound and 14 pounds to a stone, or the other way round).
This is a complete mess! We need to start again and align ourselves with the rest of the world.