Whatever unit of measurement was used on the CAD or hard copy drawing is the one which should be used when manufacturing and checking the parts. All computerised measurement and computerised manufacturing equipment can be used in metric and imperial, there’s no excuses.
From that article:
"Britain and Ireland officially use the metric system, but imperial measures are still often used alongside their metric equivalents. Under the EU decision, they can retain miles on road signs and pubs may continue to serve pints of beer. ***Other goods must be sold in metric quantities****, but retailers can also display imperial equivalents."
