Not in the U.K. Although they tried to make us fully metric starting in the mid 1970s, it didn't happen.
Items sold in shops by weight or volume are now sold in Kg or litres but all of our road signs are in miles or yards and the speedometers in our cars are in MPH.
People of around my age (mid forties) and older tend to use both systems for distance measuring. If I am designing or building something small I will use millimetres. If I am working on a house it will be in feet and inches.
Where metric measurements for distance are used here, it is millimetres and metres. The centimetre is hardly ever used and the decimetre is even more scarce.
As a Brit living in America I seem to use 4x5 and 5x4 to suit my audience. That's true of many terms - 'lift' vs. 'elevator', 'street' vs. 'road', but not when I'm driving 8-)
I was in the car with a fellow from Australia and two other local people. Speaking to the Aussie, I asked him to put something in the boot, knowing that they refer to the trunk as the boot. He got me right away, the other Americans in the car were confused and it required and explanation.
No. Hopefully you drive on the right which is the proper way to do it regardless of which country you are in!
The side of the road depends what's on the drink menu of course.
I was a PAX with a Colombian pilot driving, (Avianca, flew 757s) when he almost drove into the bar we just left. He was driving on the left (this was between Medellin and Rio Negro) when a truck appeared coming right at us. Luckily he lost control and we left the road altogether and he found the breaks.
Soon after that I think he put in a resume for British Airways.