It's not a case of any country "taking the lead". The conditions in the skies above any country are different to those in neighbouring countries, and I presume that the specific conditions over Germany now make it possible to lift certain restrictions in that country.
Was a figure of speech... Wasn't intending to appear as if it was a true "race".
However, Met predictions show Germany in a slightly MORE affected area than UK at the current time... So, if planes are getting through without incident, one would hope that at some point other countries in same "degree" of affectedness may follow suit. Clearly, safety is primary concern, but perhaps this loosening of restrictions will provide anectodal evidence that other more cautious countries are looking for to justify their own opening of airspace....
And last I checked, the cloud couldn't discern what country it was over... highly doubt it changed density/altitude at the border....
But ya never know...