In each case, nationalist parties won a clear plurality of seats from their countries' respective delegations, which are only 74 and 73 strong to begin with, respectively. It is a strong vote of displeasure from the citizens of France and the UK in sending nearly a third of their parliamentarians from parties of the right to raise hell over the Euro.
Ambrose Evans-Pritchard thinks this means it's curtains for the EU, here:
The EU authorities are now in a near hopeless situation. The logic of EMU is a further erosion of nation states. The "Two Pack", "Six Pack" and "Fiscal Compact" are all coming into force, and national regulators are losing control over their banking systems. The euro will inevitably lurch from crisis to crisis without some form of fiscal union and debt pooling. Yet voters have just let forth a primordial scream against any further transfers of power.