ChrisN
Why would ATC monitor 20-30 gliders, even if they had the capability? I would suggest that any gliders, or any GA, outside of regulated airspace would be filtered out due to clutter.
bluskis:
May I refer the right honourable poster to the post I made this morning in the thread entitled 'Mode A code shortages'.
In a nutshell, don't expect Mode 'S' in UK anytime soon 'cause ATC cannot use it.