The Weights and Measures Act 1985 (as amended) is the primary legislation laying out the units of measurement, weights and measures lawful for use for trade. It also lists certain units which may not be used for trade except as supplementary indications, which includes the aforementioned cubic yard but no reference to pole.
In any event the Act is in line with EC Directives which requires that where approved imperial units are used the equivalent metric units also be (more prominently) displayed.
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Some imperial units remain available as the primary system of measurement for certain specific uses;
i. pint for sales of draught beer or cider and for milk sold in returnable containers;
ii. mile, yard, foot and inch for road traffic signs and for related distance and speed measurements;
iii. foot in aircraft heights and any other units used in the field of air and sea transport and rail traffic, which have been laid down in international conventions etc (Article 2 of Directive 80/181);
iv. nautical mile and knot for sea and air traffic;
v. troy ounce for transactions in precious metals;
vi. acre for land registration