If you are considering installing CCTV in or outside your property you need to do some research to find out which system is best suited to what you need. If you just want one camera, then the cheapest system is probably an IP camera which costs around £40. This simply connects to your WiFi and usually has memory card inside which will store a certain amount of footage. Once the card is full, it will start re-recording over the oldest footage. These cameras have an app that allows you to view the footage when on your phone or tablet.
If you want multiple cameras and would like to store more footage then you might pick a multi camera system that has a hard drive included. This will allow you to store more footage and often the cameras offer better quality images and night vision. You need to think carefully about where you store the hard drive as it needs to be somewhere that is not easily accessible. You do not want it to be easy for a thief to be able to unplug the box and take it with them or damage it, destroying the evidence. Very often people install the hard drive in their attic, which will not be easy to access. Again most of these systems allow you to view footage on a tablet or phone through an App.