On April 14, the Home Office published its annual bulletin "Police Powers and Procedures" containing information about the number of breath tests undertaken by police forces and the number of fixed penalty notices issued. It is interesting to note that in 2010 the number of breath tests fell by 11% and the number of FPNs issued for speeding offences fell below one million, possibly a reflection of the growing use of speed awareness course for first time offenders.
The data can be accessed via the link above. However, please note that it has been published in a different format this year with much more statistical data provided in the accompanying tables. These allow comparison of forces by year for specific offences and with other forces.