Try searching the TTRB with lifelong learning and then narrow down your search by subject/educational level using the left hand menu. Using simple keywords is much more effective that typing in the whole phrase. By doing this I found an E-librarian question on this topic - see link below - which includes some books, online reports and e-resources that you may find useful.
Sport England has some useful resources on their website, including some surveys, case studies and general information about participation. See links below.
You will find research reports and journal articles by searching online databases such as the British Education Index - I have included some examples below. For full text journal articles you will need to contact your university/college library.
I hope this helps.
Physical Education Lifelong participation
Understanding participation - see list of documents at the bottom of this webpage relating to participation in sport.
Active People Survey
Maintaining Participation at KS4 (Secondary)
British Education Index
KEYWORDS: physical education, sports, participation, participation rates.
Children and young peoples participation in organised sport. Omnibus survey. Publisher: Great Britain. Department for Children, Schools and Families, 2009, pp. 39, ISBN: 9781847754967. Fraser-Jen, Ziff-Ali.
Who is physically active? Cultural capital and sports participation from adolescence to middle age - 38-year follow-up study. Physical Education and Sport Pedagogy, October 2008, vol. 13, no. 4, p. 319-343, ISSN: 1740-8989. Engström-Lars-Magnus.
Physical education, youth sport and lifelong participation: the importance of early learning experiences. European Physical Education Review, October 2005, vol. 11, no. 3, p. 220-238, ISSN: 1356-336X. Kirk-David.
Physical education, lifelong participation and the couch potato society. Physical Education and Sport Pedagogy, May 2004, vol. 9, no. 1, p. 73-86, ISSN: 1740-8989. Green-Ken.
Lifelong participation, physical education and the work of Ken Roberts. Sport, Education and Society, October 2002, vol. 7, no. 2, p. 167-182, ISSN: 1357-3322. Green-Ken.
Physical education, partnership and the challenge of lifelong participation: a shared goal for the 21st century? British Journal of Physical Education, Summer 1995, vol. 26, no. 2, p. 26-30, ISSN: 0954-6693. Green-Ken.