There's no specific law against many motoring practices. For example, there is no law stating that you can't drive along the right-hand-side of the road. If the police see you doing it they must decide whether it constitutes 'dangerous driving', 'driving without due care and attention' or 'driving without consideration for others'. If none of those apply then driving on the right-hand-side of the road is perfectly legal (as, for example, when a milkman does it, while making his deliveries at 5am on a well-lit and otherwise deserted road).
Similarly there is no law against making U-turns (except where there are specific signs prohibiting such actions).