//I can't see, for example, the London gangs staying subservient for too much longer.//
Do you really believe that the "London gangs" - whose members would not think twice before knifing or shooting somebody who upsets them - will stay off the streets because of the threat of a £30 fine? Not far from me lives a drug dealer. His business has not seen any interruption whatsoever because of the lockdown. He has his supplies delivered by the usual pair in a BMW once a week. He sets off in his own car to make his rounds and customers call on him for their supplies. Sometimes his customers will linger for a chat inside one of their cars, often with another passenger alongside. The idea that the usual suspects are all tucked up in their homes, venturing out only with a "reasonable excuse" is quite fanciful.