... the indication of the nominal weight and/or nominal volume of the contents expressed in SI units of measurement in accordance with section 3.1 of Annex I to this Directive shall, if the United Kingdom or Ireland so desires, be accompanied on their national territories by an indication of the equivalent value in imperial units of measurement (UK), calculated on the basis of the following conversion factors:
1 g = 0.0353 ounces (avoirdupois)