There are glider pilots here; those more active than I will tell you that some (many?) clubs have various scholarships and support for students and younger members, so you shouldn't have to feel like a shoot amongst old trees, although as you have gathered the pilot population overall isn't youthful, by any stretch of the imagination.
Were it probably not a practical idea, I'd suggest going to France where youngsters are far more in evidence...
But don't let us wrinklies deter you; join the club that makes you welcome and enjoy the flying. I'd make that top priority, rather than the age of the members. New friends come in all sorts of age groups and you also have the chance to set an example to your friends and drag the average age down.