In the UK, there is no such thing as a "gliding Licence" and you do not need one to fly a glider. Insurance provides the regulation and, as long as you can get the obligatory third party cover and a medical, you can fly. You will need Gliding Certificates (A, B, Bronze C or Silver C to get insurance)
As a PPL who is over 70, I believe and hope that I can go on as long as I have a medical, the desire and, of course, the money.