Dutch GA is somehow special and would fall from the sky whereas UK GA can continue to fly unaffected...
Yes, this will prevent many a glider from having an engine failure today...
Follow the deadly ash cloud here:
Eruption of Eyjafjallajökull Volcano, Iceland : Natural Hazards
Even better, watch it live here:
Eyjafjallajökull frá Hvolsvelli
Just add two days and you'll know if your flight wil be cancelled.