I have no gliding experience, but as far as your licence goes, you can fly TMG or SLMG aircraft under the privilages of your current SEP rating. All you need is a TMG/SLMG instructor do conduct some differences training, and have them sign your logbook when they think you are ready. However unless you have the TMG or SLMG rating on your licence, you cannot use the time in either of these to revalidate your SEP by experience.
I know this doesn't answer much of your post, but hope it helps a little.
HB