Interesting article from the BBC about the causes of the wet summer.  The main reason being the failure of the jet stream to head north and dump all its rain over the North Atlantic and Scotland.  Instead the jetstream has headed over the centre of the UK bringing in a series of low pressure systems. 

What's a jet stream I hear you ask! 

Jet Stream

The jet stream is a current of fast moving air found in the upper levels of the troposphere
which blow from west to east due to the Earth's rotation. This rapid
current is typically thousands of kilometers long, a few hundred
kilometers wide, and only a few kilometers thick. Jet streams are
usually found somewhere between 10-15 km (6-9 miles) above the Earth's
surface. Wind speed within jet streams can range from between 50 -and
300 miles per hour. The position of the jet stream denotes the location
of the strongest temperature
contrasts between different latitudes on the Earth surface.
Consequently, the strongest jet streams usually occur during the winter
months, when large temperature differences exist between low and high
latitudes. There are two main jet streams – the subtropical jet stream
at about 30 degrees latitude and the polar jet stream at about 60
degrees latitude.