The Home Office publishes data on misconduct/gross misconduct investigations involving officers and staff annually for the 43 police forces in England and Wales, including outcomes following those investigations. The latest statistics can be found in the misconduct section of the “Police workforce, England and Wales” statistical bulletin: https://www.gov.uk/government/statistics/police-workforce-england-and-wales-30-september-2018
Equivalent data are available for the past 2 years. Data for previous years are not held.
The Home Office does not hold information on the length of misconduct investigations, the length of suspensions, the outcome of suspensions, or the public cost of such suspensions.