On Wednesday 28 November 2012, slightly after 9.35 pm, GMT, the British Geological Survey recorded a Magnitude 2.1 Earthquake at a depth of 7 km, about 6 km north of the Cumbrian town of Ambleside, at the northern tip of Lake Windamere. This is too small to have caused any real danger, but was large enough to be felt across much of Cumbria.
The epicentre (place on the ground surface directly above the point of maximum movement) of the 28 November quake and locations where shaking was felt and reported. BGS.
As a rough rule of thumb Earthquakes become more frequent in the UK as you move to the north and west. This is due to glacial rebound; during the last ice age (i.e. before about 10 000 years ago, much of the north of the UK was covered by a thick layer of glacial ice. This pushed the rocks of the British lithosphere down into the underlying mantle, and, now that the ice has gone, these rocks are slowly rebounding, causing the occasional Earthquake in the process.
However this is not the full story, and Earthquakes in the UK can seldom be attributed to a single cause with confidence. Britain is also subjected to tectonic stresses caused by the expansion of the Atlantic Ocean, the impact of the African Plate into the Eurasian Plate from the south, and, to a lesser extent, by smaller areas of crustal expansion beneath the North Sea, the Rhine Valley and the Bay of Biscay.