@Walter Hinteler,
The Mail and Express have been major Europhobes from the off. The Mail hasn't found a European statesman to admire since Adolf Hitler. Euroscepticism has been the loudest voice on the issue for a long time.
It's only recently that people are being made aware of the advantages of staying in Europe. The graph you show is very encouraging, it shows people are starting to get informed.
Apparently, prior to the last referendum on Europe, Eurosceptics had the polls right up until the actual debate when we voted to stay in.