After a decent (but low cost) rear view camera, to install into my octy estate. Had a few close calls with old people reversing out of car park spaces, so need a bit of peace of mind. 

 

I've currently got a dash cam wired in through the fusebox and don't really want to swap it over for a dual-camera.

 

Can anyone recommend a decent one for less than £30?

May cost a little bit more, but you could always wire in a normal dashcam on the rear screen. Take the wires through the tubes at the top of the boot hatch. You can wire it into the ciggy lighter in the boot, as this should be permanently live.

 

You're not going to get a great camera for £30.

I had no success with several cheap cameras as they all wiped out the DAB signal.