Which data points?
"Drought warning in England is normal for December suddenly?
How about February in 2006? http://news.bbc.co.uk/1/hi/england/4719748.stm so yes not all of a sudden.
However, you really need the actual data to view wether this is as a result of climate or other factors.
Number of water users from 1900 to 2011 (I think that you will see a significant increase in residential and commercial water users over the past 30 years).
How about water consumption rates yearly over the past 100 years even the uneducated can see that we all use more water now than we did 40 years ago. As kids we used to have a bath once per week whether we needed it or not!
Number and volume of water storage facilities in the South East? I can think of a few that have been filled in and built over. It was a good revenue generator for the Privatised Water Companies.
Volume of leaks as opposed to percentage. If the utilisation goes up and the percentage stays the same or reduces the volume could still be increasing.