I have a bullet cam and DVS recorder. Cam needs 12v which is fine but the DVS only wants 5v.

How do I go about reducing the 14.5v when running down to a stable 5v??

Steve

you could always buy a 5v voltage regulator from somewhere like Maplins?

Search for LM7805 (5v regulator) - ideal bit of kit, should be able to handle >14v input (might need a heatsink or bolting to a bit of ally tho)

I have fitted a cigarrete lighter and plug in a 240 volt converter so I can use the standard charger,

No point building something like this to be honest, you can buy multi-voltage car adapters fairly inexpensively e.g.

DC CAR ADAPTOR/ADAPTER 1A/1000MA 3V/4.5V/5V/6V/9V/12V

For a higher current version:
DC CAR ADAPTOR/CONVERTER 2100MA 3V/3.3V/5V/6V/6.5V/7V