Some component clarity

I think I am now settled on SRAM shifters, purely for the additional multi-shift capability (3 steps) over and above the Shimano (2 steps).  Having crunched some numbers the cassette that best fits my needs is going to be 12-27 which will necessitate a medium/long cage on the rear mech.  That compbination of 3-step shifts and reasonable ranged cassette should mean that if I get caught having to stop at traffic lights when I am on the big ring two full pumps will get me from a cruising gear down to something I can pull away in.  Alternatively if it is stop-start round town I can just drop down onto the small ring and dance around the top end of the cassette.

On the practicalities side I have discovered that Tubus do a rather nice lightweight titanium rack called the Airy.  The price is pretty eye-watering though so I may have to make do with a cheaper and much heavier alloy rack.