Changes made by Motor Vehicles (Variation of Speed Limits and Speed Limits on Motorways) (Metrication) 1981
S.I. 1981/1372
No changes made by Motor Vehicles (Variation of Speed Limits and Speed Limits on Motorways) (Metrication) 1981 are recorded.
From legislation.gov.uk's record of changes, the official one: see it there.