Voters mean people who vote. That is what you were talking about, whereas the chart was referencing party members. Looking at your post...
...you clearly have misunderstood. You are trying to use the Euro Election results to discredit a poll about party members, who are a very small proportion of Euro Election voters.Something not quite right with these graphs. perhaps the sample was only taken inside the M25.
What I take from these graphs is that the labour vote migrated to the Lib dems and Greens ( Remain) whilst the conservative vote migrated to Brexit (Leave). However, in the labour heartlands of the North of England, there was a significant vote away from Labour towards the brexit Party which is why the brexit party came top in virtually every constituency. So what we have here is another southern poll all about the South East of England.
I guess you still don't get it so let's leave it there.