A BBC Forecaster points out that the tracks of most depressions(which bring unsettled conditions) have followed a route across Southern England during much of April, May & June (to date).
This track, much further south than normal, is largely dictated by the position of the JET STREAM, a band of very strong winds at high-level, which play a major role in determining our overall weather..These winds are responsible for steering low pressure systems on particular tracks from the Atlantic into Europe.
Normally, the Jet Stream is located north of Scotland, giving winds mainly from a westerly quarter over Britain & bringing the least settled weather to N.W. Scotland & the most settled to S.E. England.
When the Jet Stream takes on a more southerly route, occasionally even into the Mediterranean, the weather can become quite "topsy-turvy", with huge departures from normal.
The key to accurate long-range or seasonal forecasting is thus very much to do with just what  position the Jet Stream is likely to take up. Things can sometimes be very sluggish, meaning that once a pattern is established, it can stay put for long periods.