Additionally, ADS-B is a world-wide adopted standard for the next generation surveillance.
Have you told the UK Civil Aviation Authority about this? They are pushing Mode S as the future.........
When I last spoke to them about ADS-B vs Mode S, they made it clear that ADS-B would only work with a fully certified (and expensive) GPS and we wouldn't get much change out of £7k.
As they can't get Mode S sold to low-end users at £1.5k, especially glider pilots, they'll have a job getting us to pay for this. It's why FLARM is working well in the UK and, for some time, will become the de facto standard.