Your question has largely been answered by others but I'll point out that large parts of motoring legislation are based around 'general' offences, rather than specific actions.
For example, there is no law which specifically states that you can't drive on right-hand-side of the road. If the police see you doing it, they (together with the crown Prosecution Service) will have to decide whether your driving qualifies as 'driving without due consideration for other road users', 'driving without due care and attention' or 'dangerous driving'. If, say, they saw a milkman driving his milk float along the right-hand-side of a deserted road, in order to make his deliveries at 5am, they would probably decide that his actions didn't fit into any of those categories, meaning that he was driving perfectly legally.
Similarly there are no specific laws regarding clothing or footwear while driving. If the police found you wearing flip flops they would have to decide (with the assistance of the CPS) whether there was a reasonable chance of a successful prosecution for driving while not in full control of the vehicle. Unless you'd just crashed your car, and told the police "It's all because of these damned flip-flops" they'd almost certainly decide that it would be impossible to obtain a conviction.
Chris