One theory I've seen mentioned is its due to the Jet stream moving more south than it normally is normally at this time of year it should pass more north of the UK helping to take the weather systems above the UK.
Just this year the Jet stream is moving over the top of the UK and so the weather systems are moving directly SW starting with UK then any bits of Northern Europe on the route and dumping all the rain on us

Its also been mentioned its a La Nina year so the colder than normal surface sea temps off of peru could be affecting global weather/jet stream patterns.
I'm no expert at all just a passing interest in weather due to being a surfer.
Wish it was winter this was snow instead
