I spoke to a radar controller and a member of NATS in the South of England today and although they cannot stop VFR flights they recommended NOT to fly any GA flights. Listening in on the RT with the same controller after midday they made a point of saying "....the pilot must ensure safeflight etc" with a big emphasis on the word safe.
The Metoffice is also showing ash from the surface upwards covering the entire UK now.
Also speaking to an engineer today, he said any volcanic ash that gets into the cylinders is like sand/grit and will wear the engine.
All because the skies are blue does not make it safe to fly. There is no way a GA pilot can ensure the flight is safe when ash is reported from the surface upwards so they should not be flying.
If in doubt still speak with the Metoffice for their opinion before flying.