In a nation that works on miles as its unit of measurement for roads, we have a further problem when some organisations insist on using kilometers - especially TV companies.
I do accept the inevitability of kilometers eventually replacing miles but would suggest a 15 year transitional period with kilometers gradually added onto all NEW road signs in brackets. A further 10 years with Kilometers as the main on all NEW signs but with miles in brackets.
To do it fairly for older people, this entire process should take a full generation.
In weights - I do appreciate how many goods are sold today in bags of 454 grams (1lb). That helped many.
Incidentally, living part of the year in Spain, I have no problems whatsoever with any metric units.