Worth a bit of historical background here.
In 1997 ICAO (note not JAA or CAA) passed an amendment to SARPs to require all aeroplanes and helicopters to carry pressure-altitude reporting (Mode A/C) transponders from 1 Jan 2002. It was passed in conjunction with ACAS/TCAS requirements for commercial transport aircraft, the idea being that there's not much point in mandating ACAS if the object they are trying to avoid can't be detected by the ACAS.
There's also a European push towards Mode S rather than Mode A/C. There are two underlying reasons for this: a lack of sufficient Mode A codes for airways flights, and a crowding of the radio spectrum which means that Mode A/C starts to get unreliable. Mode S has many more codes and is selective, so it doesn't suffer from the crowding issue.
We are two years past that ICAO deadline, and it hasn't been implemented in the UK -- it has in most other states. It was delayed because the CAA believed that it was an unreasonable burden on operators of aircraft without a transponder to require a Mode A/C transponder that would only be replaced a few years later by Mode S.
Trivial, baseless requirements don't get through ICAO. The requirement for transponders was a recognition that see-and-avoid just doesn't work well enough for modern aircraft travelling at modern speeds, and that an automated system is vital. UK airspace is as complex as it is because it is set up to separate most of the fast moving traffic from the bimblers, though that's precious little comfort for pilots trying to reach regional airports outside the airways structure.
BTW, the US is always held up as a champion of the freedom of the air. The requirement for Mode A/C transponders within 30 miles of major airports have been in place for more than 15 years. If they were implemented here they would affect most of the southern UK, as well as significant parts of the rest of the country -- for example, you wouldn't take-off from Barton without a transponder.
Whether you like my cycling analogy or not, equipping to allow your aircraft to be detected by others is going to be the price of entry into any airspace in the 21st century. Wake up and smell the coffee.