But not sure I am reassured, if there are 40 + gliders at variable heights, and directions, not talking to ATC, and possibly ahead of me. Roll on mode "S" for ALL aircraft I say.
Neither of the above would achieve anything, so wishing for it is a pointless exercise.
From the ATC point of view - you can't avoid what you can't see. If you don't like that then get an IR and fly permanently in Controlled Airspace where it's a known traffic environment. Think yourself lucky the UK attempts to provide some form of service in Class 'G' airspace - most others either say 'you're on your own' or make it Class 'E'. That would be an end to people flying IFR without a clearance which you can do in Class 'G'.
Listen to London info on a good summers weekend - the frequency's clogged up with a lot of transmissions which are pointless and unnecessary, stopping them from doing their proper job by idiots who think talking to someone alleviates them from the responsibilities of good airmanship.
From the Mode 'S' point of view - again, it wouldn't achieve a great deal. Is your aircraft going to be equipped with TCAS II v7 or better? I doubt it. So once again you're relying on the guy on the ground to point it out to you. What if there isn't one? (I can think of several big holes in the area you fly in - especially at weekends).
You have to understand the nature and supply of ATC in this country before you can sweeping statements like those above. If you're not in that position it's best to say nothing I'm afraid. Also if you have some axe to grind about the gliding community maybe looking at your own 'modus operandii' first and seeing if there are any flaws there is a better way to start.
(Apologies for taking the thread off topic)