It is very clear that the recent council elections enabled the electorate to register their annoyance with the two main parties by causing both to lose a staggering number of seats. Another fact to take away from this is that the opposition party also registered severe losses instead of the gains to be expected from mid term elections.

If the MEP elections occur it is by no means certain how the protest will be registered. There will be a Brexit party standing and they are way ahead in the polls. The big unknown is to what extent the protest vote and Brexit popularity will translate into seats. I see no way of making a safe(accurate) prediction. It is also very difficult to be certain how much positions have changed since the referendum, if at all.
The changes in percentages from poll to poll are all within the error bar so trying to make any kind of reasonable prediction is a bit of a non starter.
I thunk it will have to be simply a wait and see exercise until the votes are counted. I hope brexit will wipe the board but this is by no means a certainty.