Don't worry about it, just worry about paying for it.
I moved to NZ shortly after they 'went decimal' and all the cars I could afford were in MPH and gallons, etc. I put two felt-tip marks on the speedo,(having been paced by someone in a new car) and then forgot about it. How many speed-limits do you need to worry about?
As someone said up there, wood measures are nominal, for planed timber anyway, as they are 100x50mm (4x2 substitute) only for rough-sawn, and that is likely to be up to 3mm out. After planing and gauging it is 97x47mm or thereabouts, depending on the source. 2.4m x1.2m wallboard. A yard is a 'bit' less than a metre. No problem.
I did understand, though, that the reason that the world used to drive on the left side until Napoleon's Empire is that it was demanded that way by waggoners and coachmen. Right-handed people use their whip in that hand and could use it better down the side of vehicle. This was confirmed to my satisfaction by watching Hollywood movies.