Ok, as someone who lived through most of this historical stuff, my view and answer to the key items AFAIK is:
The UK went through a period of "metrication" where all official weights and measures were metricated, hence the issue about selling things in kg and g instead of lbs and ounces, etc . There is a permanent get out for beer which is sold in pints / half pints and distances on roads / speed in miles per hour. The discrepancy between people telling you things in imperial or metric is essentially one of age. Those 40 and under were only ever schooled in metric and hence tend to use those units all the time - the only exception seems to be the weight of babies which although "officially" measured in kg is announced to the world in lbs...)
Decimalisation referred to the change in currency from 12 pennies to the shilling and 20 shillings to the pound, complete with strange coins such as the "threpany bit" - 3 pennies and a 10 shilling note - to a decimal system of 100 pence (initially called "new pence") to the pound, all of which were coins, thought he 1/2p was always a problem and disappeared a few years later.
This occurred on a single day in 1973, though of course a dual system existed for some time after to cash in old coins etc.
The issue between US units and Imperial units is still a key one as there are some considerable differences and I still ask people are they using US GPM or imperial GPM as they are quite different. Length and weight seem to be the same, but not volume for some reason....
BTW if you want official designations of SI and conversions BS 350 is an excellent document - interestingly it now calls imperial units "UK pt, fl oz etc" and quotes 1 UK gal to a US gal at 1.20095 US gal to the UK one.
Interestingly Ireland has, over the 20 something years I've been visiting, changed gradually from miles to km and km/hr as new roads and systems were built using EU money and is now virtually wholly metric. If you saw a dual sign in the UK it was an error, although many trucks and buses have signs saying they are limited to xx km/hr as these are EU wide speed limits (trucs are 90km/hr - 56 mph). Al lot of roadwork signs are now in m as it's pretty much the same as a yard when you're talking those sort of vague distances.
The beer / foam issue arose about 19 years ago when the new labour government came to power and initially promised to pass legislation so that you got a full pint of liquid plus a head. However despite personally writing to the deputy prime minister to ask what happened, it seems the lobby powers of the brewers, who then normally only sell 90-95% of a pint had prevailed. It is common to ask the person serving to "top it up" when the foam has reached ridiculous levels, but 1/2 " (1cm) is common.
we've drifted off the original topic, but this is much more interesting!
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
![[cheers]](/data/assets/smilies/cheers.gif "[cheers] [cheers]")
