Fans of archaic unit systems may find solace in the fact that astronomy still stubbornly resists the onslaught of SI units. The CGS system is still king in astronomy: ergs/cm^2/s is our preferred unit of flux (except radio astronomers use the Jansky) and we also like such non-standard units as the Angstrom for wavelengths, light years and parsecs of course for distance, and arcseconds and arcminutes instead of radians for angular measures. In the astronomy articles I've written for Wikipedia, though, I think I've stuck with SI except for light years and parsecs.
As for what UK folk use, well, the packets might be marked in metric but the amounts are still imperial. We buy milk in 568ml (pint) bottles, peas in 455g (1lb) packets, that kind of thing.
Not sure that changing distances on road signs would be that difficult or at all dangerous, it's just that being on an island we have no compelling reason to conform to the continental standard - there would be no benefit to be gained from a switch.
-----Original Message----- From: Tony Sidaway [mailto:minorityreport@bluebottle.com]
In the UK this is only for "folk" uses such as pints of beer and road signs. I believe all scientific and engineering ventures switched to SI long ago, and nearly all commercial institutions (aforementioned pints of beer excluded, for instance) are required to use metric measure although they are also permitted to provide equivalent ounces, pounds, stones and whatnot. They sell orange juice in liters, butter by the kilogram, cloth by the meter. Liquor is sold in metric measure, so in a pub you get a pint of beer but a 35 ml measure of brandy, and a 200ml glass of wine.
Road signs haven't switched because it would be very difficult and dangerous as well as politically explosive.