Given the BGA material for SPL and LAPL(S) is still aligned with EASA, the Easy Access Rulebook for Sailplanes gives info on the requirements for, and privileges of the TMG Extension as well as currency requirements. Some advice for this document: search key words in the "table of contents" first and then click the relevant section to snap to that bit of the document.
Summary of Requirements - Courtesy of Motorglide.co.uk.
BGA TMG Extension Course Programme - This includes the checklist of all the exercises in the syllabus as well as recording First Solo, Theoretical Knowledge, Qualifying XC preparation and then completion of the course and readiness for test.
Qualifying Cross Country Form - For authorising, recording and completion after the qualifying XC flight.
Skills Test Report Form - Self-explanatory, but for recording the administering and outcome of the skills test. This is also included as a checklist on the following form as well.
Application via the BGA to the CAA for the TMG Extension form - Requires minimum training requirements to have been met, as well as skills test with a pass (Skills Test Record is also included on this form so may not need the one above), as well as your SPL/LAPL(S), TMG Training Record (ie the Course Programme) and a scan of relevant logbook pages and medical before this can be sent off.
Privileges and conditions Click here for CAA page and note requirement for 10 hours and 30 launches PIC before carrying passengers
I am indebted to Stefan Astley (at LGC) for the above helpful information
SPL TMG ROLLING RECENCY
Holders of SPL TMG privileges are reminded of the TMG 24 month rolling recency requirements at SFCL.160, which include a training flight of at least one hour total flight time with an FI(S) TMG.