It also depends on how bloody-minded the inspectors are...I was lucky enough never to be quizzed about washers, for MOT or when importing a car. However, I was told to have a speedo in miles instead of km/h by the DVLA inspector, when I imported my 59, last December.
Robin Allen who is himself a DVLA inspector, subsequently told me that the inspector had absolutely no right to ask for this and to fail the inspection on that basis. This only applies to cars less than 10 years old.