Chris is right.
The most irritating thing the CAA have been saying is that they are taking a leading role in the development of a low-price/low-powered Mode S.
When you ask just what they are doing about it, they have to admit they are able to do very little, and are leaving it to the market. BUT, by introducing the mandate, they are creating the market.
There is still little sign of the sub-£1000 Mode S that is the aim of the Mode S team and the limiting factor for them to implement full Mode S carriage.
Oh, and watch out for a little nasty in the Mode S document - there may be out-of-phase intoduction of Mode S for international flights.