i don't know a thing about your hobby Kevin, why has someone decided that theirs a need for gliders to have a tracker fitted
There are pages and pages of boring consultation documents on the subject but the long and short if it is that whereas currently commercial air traffic uses controlled airspace to which gliders, prvate aircraft, hot air balloons, microlights, hang gliders, etc. have no or very limited access the plan is to allow us both to share the same airspace.

This requires them to be able to reliably identify and track anything that flies in open airspace in the UK by radar, and route commercial aircraft away from it, hence the requirement to fit transponders.
This is being justified on the basis of a huge projected increase in commercial air traffic - so it'll really fit in with the government's commitment to halting "climate change"!
The other argument is that it will allow commercial airliners to fly much shallower approaches to major airports, saving them some fuel but meaning much larger areas of the country will be subject to low flying jets than is currently the case.
The hidden agenda that they won't admit to is that the government are committed to development of UAV (pilotless aircraft, which they'll no doubt use to spy on us). These clearly need to know what's around them because the pilot, and his eyes, have been removed from the equation. I suspect the prospect of robot aircraft flying around would not win them much public support, hence it being hidden.
So, we shell out £7k per aircraft (more than many gliders are worth), assuming it's even feasible to run this equipment from a battery (a glider has no other source of power) and the only benefit is to the airlines and BAA's coffers.

We won't be receiving information from air traffic control so there is no safety benefit to us. They could sit and watch 2 gliders collide on a radar screen without being able to do anything about it.
Meanwhile, the gliding community has developed a system that can give real collision avoidance at a cost of 400 quid per aircraft.
Anyway, going way off topic now but as you can see this makes the road tax situation look positively inexpensive.
Kevin