Sorry, having asked the Madone 4.9 v 5.2 question, I decided to buy the 5.2: then I saw a Colnago CX-1 Evo which looks like a very good frame which is at least comparable with the Trek but comes with the Di2 gear set. The wheels are also ok for an off the shelf bike (Shimano R80s) and overall it looks like a lot of bike for the money.
The Colnago is advertised as reduced from 4,999 to 3,250 and I have seen it being sold elsewhere (on the internet) for 4k and the frame on its own for 2,400. This looks like a good deal. Only problem is the deal is via the internet and I can't find any local shop that sells them.
Any views on this bike and how it compares to the Trek would be appreciated. Trek dealer suggested the Colnago geometery is more aggresive and so would be less compfortable over longer distances (obviously he would say that!).