For those who queried my earlier post here is a quote from the DLTR (now DfT) annual report 2002.
10.56 We also contract the CAA to undertake various tasks, including the investigation and prosecution of breaches of aviation safety legislation, work to ensure the safety of foreign registered aircraft and advice on aviation safety to the UK’s overseas territories.
I don't know what happens to any costs that the CAA receive but my guess is that it is "reinvested" in further enforcement activity.