WHICH planet is Mr Garnett on?
He states that the metric system is not yet the standard of measurement in Worthing and that the majority of your readers can't immediately visualise what 20cm means.
This is a topic which I have studied a great deal but I shall restrict myself here to two comments.
Firstly, we live in a world that is virtually 100 per cent metric.
Everything in the modern world, except the fabric of buildings over about 40 years old, has been designed and manufactured in metric units.
This includes all motor vehicles, all buildings and their interiors, decoration, furniture, clothing, paving and all things electrical.
In fact, electrical measurements have always been metric.