just back from Holidays in North Riding and noticed that on the B1261 between East Ayton and Filey there are 2 railway level crossings, on both crossings the signs are in metric only and therefore illegal, the signs relate to large vehicles waiting and phoning before crossing, the signs are metric only and refer to "Tonnes", "Metres" only, I did not have the camera to hand though!
These signs may be in Imperial only or with metric added in brackets afterwards. See Diagrams 780A, 780.1A, 780.2A and 784.1 of the Traffic Signs Regulations and General Directions 2002 (S.I. 3113 of 2002), pages 115 and 116.