Nothing like that in the UK but socially you are expected to help and do your best up to your level of expertise. Even doctors and nurses are not trained in first aid as a matter of course and would not be expected to set limbs or do brain surgery unless that is their expertise and they had the equipment. Bu if you have the knowledge and equipment, say a defibrillator, you may use it without fear.
We have a 'good Samaritan' ruling by the courts which indemnifies you against problems if you follow the above rule.
The Good Sam laws are NOT as encompassing as suggested.
The laws typically do NOT cover whether the suit is filed, just affects the likelihood of a liability if the suit goes through completely without being settled. This means that a physician or nurse can face years of litigation. Given that SOME malpractice insurance can settle without permission from the physician, it can mean a report to the National Practitioner Database even if you are completely in the right.
There are also ways to pierce the Good Sam laws completely. As mentioned in Auerbach, "Wilderness Medicine". Going on a cruise in which you may have been offered a discounted fare (possibly even without your knowledge) may pierce the Good Sam law and open you up to the regulatory obligation of being prepared for an orthopedic emergency even if you were only a psychiatrist.
It would appear that the Good Sam laws fail to protect Doctors and Nurses as originally planned.