Can you help me identify this BBC drama from the late 80s/early 90s?

See if you can help me out with this one…

It was a one-off, coming-of-age BBC drama from the late-80s or early-90s. It centred on a boy of about 12 or 13 who was spending the summer with another family in their house in the country. The father was a doctor and had a stroppy teenage daughter, who argued with him for working in private medicine, saying that it was like queue-jumping. The daughter's rebellious, outspoken behaviour contrasted with the boy, who was very quiet and obviously didn't come from a family where grown-up subjects were discussed.

During one scene at the beach, the boy stares longingly at the daughter, although it doesn't turn into some sickly adolescent love story, thankfully. It was more about him developing adolescent urges and his awareness, through her greater maturity, of adult concerns.

Sorry, not much to go on, but it's one of those programmes that resonated with me at the time, and I only just remembered. Any help would be appreciated.