Amanda McAllister, 18, from Barrhead, Jade Bourne, 16, and Taylor Walton, 17, from Neilston, and Josh Clarke, 17, from Eaglesham, were invited to tell delegates about their work at the International Conference on Assets for Health and Wellbeing Across The Life, at the British Museum.
Their group, known as The Big ShoutER, was formed by 16 and 17-year-old volunteers to influence positive change in health and community settings.
Their presentation at the conference, The Bruce Mc Bru show – More Than Lip Service, was in the style of The Jeremy Kyle TV Show, and showed how they have contributed to the development of health and wellbeing.
Sir Harry Burns, the chief medical officer for Scotland, who is from Barrhead, joined the group on stage.
Taylor Walton, from Neilston, says joining the group in January this year changed her life.
She had struggled with her relationship with her 13-year-old brother, Logan, who is autistic but the Big ShoutER has helped her deal with issues surrounding his autism. Taylor, who is now a carer for Logan said: "I didn't used to spend much time with Logan as it would have just resulted in us arguing. Now I'm part of his life and I take him out so we can spend time together and share hobbies.
"Being part of the group has helped my life skills. I'm working harder at school and getting better grades.
"The self-belief I've gained means I've got a more prosperous future ahead of me.
"The trip to London was a once in a lifetime opportunity. We got a lot of amazing feedback."
After the conference, East Renfrewshire MP, Jim Murphy, arranged for the youngsters to spend time at 10 Downing Street, and go for a behind-the-scenes tour of Big Ben.
The group also saw Shrek the Musical, where they met Amanda Holden.