When was the first THS (Trimmable horizontal stabilizer) used and on what aircraft? Has any UL or GA trimmable stabilizer?
If the question is understood to encompass any form of horizontal stabilizer which may be adjusted in flight (with or without a separate movable elevator), then the answer would appear to be Sir George Cayley's 1849 full-sized glider which briefly took flight-- see http://www.flyingmachines.org/cayl.html. The Wright brothers also used all-moving horizontal surfaces on their early gliders and airplanes, but located in front, as canards.
However, a comment has clarified that the question is meant to only encompass a horizontal stabilizer which may be adjusted for trimming the aircraft, with an attached elevator for pitch control inputs.
According to page 9 of the book "Aces Wild" by Al Blackburn (see this Googlebooks link), the first use of an in-flight-adjustable horizontal stabilizer was in 1929 by Clarence Gilbert Taylor in his B-2 "Chummy", which eventually evolved into the Taylor Cub and then the Piper Cub, all of which used the same stabilizer trim system. Naturally, all these aircraft featured an elevator attached to the adjustable horizontal stabilizer.
The same source says that many old Waco biplanes used the same feature. In this photo of a 1936 Waco biplane, the slot associated with the adjustable horizontal stabilizer is clearly visible.
It would appear to be the Boeing 707/720, followed by the DC-8.
Lots of GA airplanes derive pitch trim and static stability from the stab surface, that is operated manually by a screw jack driven by the trim wheel, and only use elevator for maneuvering inputs (having no trim tab, it just trails when hands off). Significant ones that come to mind are the Cessna 180/85 family, the Piper Cub/Super Cub/Pawnee family, and the Mooney M20 family.
Modern airliners with trimmable stabs and hydraulic controls use a particular geometry in the elevator control linkage (or by software if FBW) at the control linkage interface between the horizontal stab and and vertical stab that always keeps the elevator actuator linkage neutral position aligned with the stabilizer chord line, so the surfaces are always hydraulically maintained in stab chord alignment in the absence of a control input.
The result is the trimmable surface becomes the entire stab/elevator unit, not just the stabilizer. As well the control stick neutral position in the cockpit never changes, which takes getting used to when transitioning from an airplane with a elevator tab for trim, where the elevator stick position changes with trim.
It was first used on Spitfire in October/November 1944 to test out the idea, and was then to be used on the 1943-designed Miles M52. The M52 was going to be a jet-powered supersonic aircraft and would have been the world's first supersonic aircraft. It's not well-known because the design was given to Bell as they started design of the rocket-powered X-1, followed by the British government cancelling the project.
The THS (Trimmable Horizontal Stabiliser) is just the Airbus name for the elevator trim. In Boeing planes it's called Stab trim. All planes have a trim on the elevator: the differences you can find is whether the trim rotates the whole elevator or only a small surface in it