Until recent redundancy I was a weights and measures inspector so know a little about this subject. Inspectors are there to ensure the correct quantity is delivered and over of under the requested quantity is wrong in w&m terms. Prosecution for over measure would be rare. All goods are now sold by weight of volume in metric quantities. However, there is an exception for beer which can be sold by the half pint or multiples thereof. Selling in imperial quantities is illegal but an indication of the imperial equivalent is OK to assist customers. Asking for a quarter of ham is also OK but the ham would be weighed on a metric scale and usually the customer can see the weight on the scale and should be told the price by the sales assistant. The 'e' that you see next to the quantity on pre packaged goods indicates that they have been packed using the average system. This means some packs can be slightly under and some slightly over as long as the average of the batch is equal to or more than the declared quantity. Fuel pumps charge based on the fuel delivered and will round the price up or down to the nearest penny. E.g. if the quantity delivered equates to 749.6p or 750.4p you'll be charged 750p. There are tolerances on the meters found in pumps and they are regularly tested. There's no such thing as a metric foot which was used in the building trade at one time for 30cm.
