Waveform data for the stations of the national network is stored in one hour MiniSEED files. MiniSEED is the globally accepted format within earthquake seismology for continuous time-series data. The files are on the FTP site:         ftp://seiswav.bgs.ac.uk The SEED manual is here. The files are divided into directories by station then year then month and the final three characters are the channel ID. The response files required to transform the data into meaningful units are also on the FTP site:         ftp://seiswav.bgs.ac.uk/dataless.
Earthquake parameters are stored in text files in Nordic format - the parametric format used with the SEISAN analysis package. These parameters include the location and magnitude along with the phase times and amplitudes used to calculate the location and magnitude. The files are on the FTP site:         ftp://seiswav.bgs.ac.uk/events The format is explained here. This is not the best way to find earthquakes in a given area or of a particular size - use the search here.