Why should I be forced to pay far more than the aircraft's value just to fit a bit of kit that I will never have occasion to need?
If you lived and wanted to fly in the US then as I understand it (could be wrong..) I think you would have to invest in a transponder at least if you wanted to fly within 30NM of e.g. SFO or other major Class B airspace so that your primary radar return did not cause grief for the radar APP controllers in that area who are vectoring IFR traffic through Class E, D & B airspace whilst permitting maximum freedom to other airspace users. The equivalent to that here would be when IFR are vectored through class G when approaching a number of airfields (e.g. Biggin).
Such a mode C veil would give you the choice of either choosing to comply by either equipping your current steed if feasible, or doing as the rest of us do and renting (or buying a share in) an aircraft type which is equipped with a transponder for flying in the more dense areas. Or, you could limit your flying to less dense areas away from the mode C veil and continue with your current type of flying there.
That would be the argument - but I don't see it happening here. Instead we seem to be leapfrogging this and forcing everyone to use mode S for little or no apparent benefit to GA. My view on mode-S would be different if ADS-B was to be part of the plan here, but it doesn't seem to be (whereas in both the US and Australia there not only clearly detailed policy goals in relation to this new form of surveillance, but there are also pilot programmes under way).
Andy