Having spent some time researching FLARM I would not rule it out yet. The system has only been around for a short time but it has huge take-up in parts of Europe and the BGA has been running tests on it, which appears to have gone very well. It is possible that the take up in the UK will increase dramatically over the next 12 months.
FLARM is available as a very small, light, portable unit with very low power requirements (or an all singing all dancing panel mount). It is the only option for the majority of flying machines in the UK which cannot fit Transponders. If the BGA push this and get the support of the BMAA then it could make a difference. There is also a version specifically for helicopters.
Rod1