here is a link to a low cost collision avoidance system
Flarm - Homepage It is only £400 and needs no maintenance. Gliders have fitted these in large numbers and it does work in aeroplanes or helicopters too. This week alone I have had numerous warnings of traffic approaching from my blind spot or out of sun.
I remember an Australian flying school that fitted a similar system (ADSB) to all its training aeroplanes years ago, should UK flying clubs do the same?
The advantages are that you don't need expensive transponders, or radar, or ATC. A complete stand alone low cost life saving device.
FLARM will also warn pilots of obstructions (masts and ski cables etc) in many parts of Europe