What is all the fuss about Mode A? When I had an aeroplane with a transponder one of the first things I did with it was upgrade it to Mode C. You don't need a new transponder, there are add ons which you can get for 200 or so quid. Make that mandatory and you lose the spurious TCAS warnings that WWW was dramatising. How many mid-air collisions (not including glider - glider collisions) have there been in the last few years? Very few that I can think of. Every aspect of safety has a price fortunately it is not my position to put a price on the risk of a mid-air in terms of mandatory Mode S etc.
I fly in the North London corridor quite often and generally call the airfields concerned to let them know I'm skirting their zones. Most of them don't seem to give a damn. I generally listen out to London Info in between calls as well. My biggest benefit though is that I usually fly during the week rather than the busy weekends..............