You dont need any kind of registration with the NHS to recieve immediate emercengy care or ongoing care related to emergency treatment.
You dont even need a registration to go into a NHS doctors surgery & have them see you, although the doctor is under no requirement to do so and even if they do see you they are under no requirement to treat you, plus of course you can be billed for any costs incurred. But still no registration is required, it is preferred but not required.
So in essence you dont need registrations, you only need a registration with a NHS GP if you need ongoing, repetative care and even then only if you dont want to pay the full costs of treatment and have the benefits that registration brings such as your GP having a medical record of your history.
Oh & the suggestion that people get copies of their medical records (which GPs are legally required to provide if asked for) isnt for some sort of protest, but it is prudent. As if you ever have a problem with the police/security services or social services any notes even unproven ones in your medical records such 'subject may drink to excess' will be used against you as many have found out to their horror/disgust/shock&loss.