I tend to agree with those who assume a scam, and I think the OP did exactly the right thing. I do remember, though, many years ago I was driving into London and was in traffic jam on the Westway. My car overheated, as cars did in those days, and I needed to put boiling water into the radiator. So I pulled off, went down a side road, and knocked at a random door. It was answered by an elderly gentleman whose accent suggested that he had been brought up in Jamaica. He invited me to sit in his hall, at a table covered with a lace cloth and family photographs, then boiled a kettle, accompanied me out to the car and poured the water into the radiator. When I thanked him, he said 'It's my duty'. I was very sorry afterwards that I hadn't noted the name of the street or his house number, as I would have liked to send written thanks.