The charts used to determine the no-fly zones are published here:
Here's how to read them: they offer four 'snapshots' in time, six hours apart. So the latest ones are for 06:00, 12:00, 18:00 and midnight today (that's UTC/GMT so add two hours for Belgium). They are revised every six hours, the first one drops off and a new one is added - so you never get to see more than 18 hours in advance.
At each point in time being measured, there are three maps: the first one id for ground lervel up to 20,000 feet, the second from 20,000 to 35,000 feet and the third one above 35,000 feet. At the moment the upper level charts are clear, which means that aircraft can safely fly above the ash. Obviously there is lots of nasty stuff in the lower levels over the Atlantic, but aircraft don't normally fly down there unless they are taking odff and landing.
You will see on the maps three zones. The black is where the ash concentration is at levels where flying is not a good idea. The red is where there is ash, but flying can be conducted safely. It may lead to extra wear and tear on the engines but that's for the airlines to make judgements about, it's an engineering and maintenance rather than a safety issue. The third zone is marked by a black dotted line and this is the buffer zone (60 nautical miles) around the black bit.
So if your bit of Europe falls within the black dotted line, you can expect airport and airspace closures. If you're in the red, you 'should' be OK, although it's up to individual countries to impose their own rules.